Ignition Repair Replacing HOWTO
1989 Dodge B250 3/4-ton Van 5.2L 318 in3

© 2010 Brian Mork


FOR SALE:  One live-tested fully working ECU PCM SBEC SMEC computer for a 1988-1989 Dodge van 6-cylinder or 8-cylinder van,  $65.
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This web page contains a narrative log and pictorial essay to fix a 1989 Dodge B250 van with 5.2L engine and 135,000 miles.  It's meant to teach you, document technical data, and perhaps most of all motivate and encourage you as you try to figure out your non-working Doge van.  I included lots of links to web resources I found useful. Chad's 1989 1-ton B350 van repair log is also helpful.  I always appreciate your link back to this page so Google thinks what I say is important!

My 1989 Dodge van with 135,000 miles was working fine, then one Sunday morning, it sparked a bit, almost started the engine, and quit.  Now it won't produce any spark, and won't run.

Before you start work on a car project that may take several weeks, consider canceling insurance or doing "storage" insurance. My insurer used to provide a "storage" option that provides only comprehensive coverage and drops the cost of a newer vehicle from $52.50/mo down to $5.00/mo.  More recently, they've changed the definition of "storage" to mean "state mandated minimum insurance," and for the Dodge van in this article that change drops cost from from $27.17/mo to $6.70/mo. Or, if you can handle the risk, you could remove ALL coverage including comprensive and save a boatload of money.
Click on any picture to see a close-up view.

Our van is affectionately known as "Big Blue". It's been across the nation at least once and we hope it has a lot more life in it! Looks pretty nice even in the cold snow.  We have loved camping in it so far, and the rear seat comes out for cargo hauling. 

Tools are stacked up behind me for easy access.

One convenience of the full-size Dodge vans of this era is that the engine is worked on from the inside of the van.  This is particularly nice during Michigan winters when no garage is available!  Water on the floor is snow melt off my boots.

Ignition parts up close.  The distributor is beige with wires coming out the top. The coil is round and lays horizontally to the right. I pulled one of the spark plugs going to the right in the picture, and could get no spark.  Finally I pulled the central cable going *into* the distributor and hooked it to a spark plug. Nothing. Not good.

3/4 view of the ignition coil and the spark plug I had out and was testing.  You can see the plug I pulled. Actually, it looked in pretty good condition. Looks like my valve gasket is leaking a bit of oil.

Coil and distributor. another view of the coil assy. See the little grey wire?  There's one on the other side, too.  They both disappear into the wire bundle, and I don't know where they go. Unscrewing the terminals is pretty easy and I did tests with wires removed and in place.

Dropping a bolt or screw down the throttle throat would be bad!  You have to remove the air filter and jostle the metal support aside to work on the twin fuel injector harness.
Inside the distributor looked really clean for 135,000 miles.  Must not be original. I should have picked up a spare cap and spinner and magneto pick up from the junk yard.  Maybe I'll go back and get them. 

With the distributor cap off, you can see the black disk in the bottom (magneto pickup), and the spinner that puts spark out to each of the 8 cylinders.
Side view.  The distributor body looks a bit corroded, but everything inside was nice and clean.  A little bit of pitting on the tip of the spinning conductor.

With the lower dashboard panel removed, you can see the black box ASD relay I was working on for 90% of this project.  Uh.. turns out that feeds only the custom interior lighting!
Having exhausted every other possible problem, I dug into the "brains".  This the the computer ECU (Engine Control Unit) or PCM (Powertrain Control Module) or SBEC (Single Board Engine Controller).
I went to the local junk yard and pulled and ECU from a year (1988) earlier 6-cylinder van.  Would it work?  I pulled the air cooling cover and compared them. Torx driver required to remove the cover.
The top plate or layer inside the computer is the higher power switching transformers and voltage controllers (heat sinks) that use the white connector.  Underneath, the fully encased computer circuits using the red connector.
1989 8-cylinder. If you zoom in close, you can see the individual IC chip numbers.  Hey, I used to use these CPU chips in other projects computer projects!

1988 6-cylinder. Only significant difference I could see was one less air cover mounting screw.
This is what turned out to the be the real ASD (mounted on the firewall).  See the little grey box? That's the corroded ASD relay that someone put into the harness.  Water dripped down the harness and collected in the relay
On the left: culprit and cause. In the middle: the interior custom-lighting switch relay. On the right: two relays pulled from a 1989 model van. They seem identical electrically, but have plastic molding that keys them into one connector or the other.
Original ASD ready to be connected to the wiring harness.  See how the relay body itselfl makes a little water-proof hood?
The ECU is connectd with three hex head bolts.  Two were badly corroded.  One snapped off when it was removed.  I was going to drill it out, but managed to untwist it with a pair of vice grips.

Original 8-cylinder ECU back into position.   The 6-cylinder ECU was in position when the van came back to life, so I know either can be used.

Thursday (4 days):

No spark. Fuses okay. Trying to figure out why there's no spark. How can I check the coil?  Where do the signals come from that go into the coil?

Friday (5 days):

I opened the distributor and played with the ignition coil. See the two terminals, with almost-red copper tips to the little bolt ends?

When I removed the upper nut and grey wire, across the coil primaries measured about 3.9 ohms (later tested to 1.6 ohms with a better meter).  I turned the keys on and the forward and lower nut was about 11.7 volts compared to ground.  Later, this was not reproducible and there was no voltage on the coil anywhere. The upper disconnected terminal was also 11.7 volts through the coil until I connected the grey wire back on.  The grey wire seems to be holding the whole thing grounded because both terminals then moved to about 0 volts.

The red wire coming out of the coil center seemed loose so I played with it.   It spun out easily, taking the center stem of the coil with it.  I disconnected the two and screwed the coil stem back in firmly with a phillips screwdriver.  While the wire was off, I measured it and I think it was about 1.4 Kohm. I seem to remember that these wires have built in resistance to cut down on ignition noise, so that seemed okay.  Chilton's books specifies a maximum of 7 Kohm per foot.  I clicked it back firmly onto the centerstem of the coil. 

I did the spark plug test again, and this time got about 5 sparks, then intermittent, then it quit doing any sparks.  I jostled the wires around and my hold on the plug and tried again.  No more sparks..  Something is marginal, but mostly not working.  No more sparks..

I couldn't figure out how to remove the spinning stem from inside the distributor to look deeper.  From a friend:

"Dwell time is a term used to describe how long (degrees angle) the points (mechanical) stayed closed.  Mechanical points stay closed much of the time (shorted to ground).  It is at the moment the points OPEN that the Spark actually occurrs.  When the points OPEN, the field in the coil collapses and causes a high-voltage spark in the secondary circuit of the coil, many thousands of volts, enough to cause your spark-plug to spark.  So........a coil is basically a step-up transformer you could say.  The AC type current you are apparently seeing at the primary terminal on your coil while the engine is rolling over is normal and to be expected.  Actually, it should be AC current in that is vacillates from zero volts to around 12 volts right?  As you said, without an occilloscope, it would be difficult to actually see this pattern with much accuracy using a volt-meter.

Dwell time in a computer-controlled system is greatly enhanced because the dwell can be increased thus providing more field saturation time in the coil and the subsequent hotter spark."  

Saturday (6 days):

I pulled the coil off and started testing things.  Across the primary tests 1.6 ohms, which matches Autozone's specs.  9.6 Kohm from the secondary to either primary terminal. NAPA had no way to test this, but let me check one of their coils.  Identical.  I think the coil is okay.  I don't have my oscilloscope out and running, so I can't see exactly what happens, but the voltage settles into an AC signal across the coil primaries, so I think the ignition module is doing something.

Oh, BTW, I let the grounding lug for the coil mount float unconnected and turned on the ignition.  When I did this, the fuel injectors go full bore ON and start pouring lots of gas down the throttle valves.  I couldn't tell what the gushing sound was, and then saw it! 
Autozone was willing to test the ignition module transistor, but I can't find it yet. I've looked all over on the firewall.  It's just not that complicated, and I can't find it.  There is a big bundle of wires going into a plastic shroud covered item about 6-8 inches across about in horizontal center of the firewall. I think it's the computer module.  I'm fearful that the ignition module is buried in the bundle somewhere, or part of the computer module. [later comment - yup, the transistor is in there].

I read on on the internet, a post about control modules from years prior:
"I have the same year and make of pickup [truck]. The problem is in 1988 depending on how early or how late in the year it was produced it could have 2 different ignition systems. If its a late model like mine it wont have an ignition module. Late models ran a hall effects pick up in the distributor. Which just relays a signal to the computer and tells it when to ground the coil to send spark to the distributor. But on the early models it should be on the fire wall or the drivers side fender well. good luck hope this helps you."

Monday (1 week 1 day):

Read how to do Chevrolet 1980s-1990s computer service codes (more authoritatively listed on the Mopar computer spec sheet, linked below).  Basically, within 5 seconds, turn the ignition power on-off-on-off-on, and then wait and count blinks.  I was getting codes 12, 42, and 55.  12 is a generic "battery has been disconnected" code that seems to always show up.  55 is a "end of message" code.  42 is meaningful, and can have several similar interpretations as listed on Alpar's web page and the Chilton manual:

I don't know that I have any trouble with the fuel pump.  In fact, when I was playing around and disconnected the high-voltage spark coil, I left a ground lug unconnected that is normally connected with the mounting screw.  Turning on the ignition in this condition fully opened both fuel injectors and flooded fuel into the throttle body.  We're talking like a shower head of spray.  I haven't fully interpreted this, but the fuel system did act strange associated with the ignition coil.

To check these codes, I unconnected the negative battery terminal while charging the battery from another car.  I unscrewed the computer covers and took some pictures for about 1/2 hour and then hooked up the negative side cable and read the codes without trying to start first.  I received 12 and 55 (no 42).  Then I tried to start and it happily cranked over and over with plenty of power, but did not fire once.  Checking codes, I am now again receiving code 42.

The local Chevrolet dealer says they have no more 1989 manuals, and so he can't advise where the ASD relay is at.  He said it should be stamped with the number "52-33-302" and costs about $28 to buy a new one.  I found two relay-box looking things bolted to the firewall.  One to the immediate side of the main computer box toward the driver side.  The second is down by the driver's right foot.  One has an obviously different number; the second has no discernable number.

Tuesday (1 week 2 days):

asd-relay-pinout

I found the ASD Relay.  It's a black box in the wire bundle up under the dash, outboard side of driver's left leg.  [Caution - read this entire article! I initially fournd the wrong relay.]  Mine has a part stamped "46385" and inked "4273307 0179".  Lots of electrical testing today.  I found an ASD relay electrical mechanical pinout diagram at dodgeram.org.  The four terminals are numbered 30, 85, 86, and 87.  Looking at the male pins of the relay, pin 30 is on the bottom and pin 87 is on the top.  Pin 85 is on the right, and 86 on the left.  Looking at the female connector for the relay, pin 30 is on the bottom, and pin 87 is on the top.  Pin 85 is on the left and pin 86 is ont he right. A textual description of ASD relay pinout is available at justanswers.com.  I posting by "dsramprat" at automotiveforums.com gives a checkout procedure for the ASD relay.

Okay.. that's all great.  Relay appears to work out of the van.  In the van, things get wierd.

White wire ignition +v on the hot side of the relay coil stays at constant +12v when ignition is on and not cranking the engine.  It drops to about 1v within a second when cranking, and then returns to 12v as soon as cranking stops. Chilton claims this is direct from the battery through a fuse link.  Another web page says fuse 9, but that did not check out on my van.

Brown wire relay output goes to +12v when the ignition is turned on.  It drops to 0 v when cranking and returns to 12v when cranking stops.  This is true with or without the (-) side of the ignition coil connected.  This is an important distinction because theoretically 12v / 1.6 ohms or 7.5 amps of current goes through the coil, and this could draw down a voltage.

Resistance checks indicate the (+) side of the coil does not appear to be connected to the brown wire pin 87 ASD relay output as shown in Chiltons.  So I'm not sure the simple circuit diagram is complete. [later note - I was testing the wrong relay; the output was literally connected to nothing]

The hot side of the coil primary behaves differently, too.  With the negative side disconnected (no load), it sits at 12v with the ignition on, and drops to about 4v when cranking.  Remember, this is without current flowing through the coil. With the (-) side of the coil connected, the hot side is never above 1 volt DC.  I don't have an oscilloscope to watch the fast time behavior, so it might be pulsing up to 12v as it should, but I can't be sure.

When the coil hot side is at 12v, the relay output is also at 12v.  In order to be sure I wasn't reversing the relay connectors, I floated the entire meter and just monitored voltage across the relay coil (pins 85 to 86).  It was 12v when the ignition was on, and dropped to 0v within a second of cranking the engine. Based on this, the relay is initially energized, and then is NOT energized as soon as cranking starts.  Output voltage is 12v when the ignition is on, and drops to 0v within a second of cranking the engine.


Wednesday (1 week 3 days):

With the relay hooked up in place in the van, I hooked up 4 jumper cables to monitor voltages.  The relay coil measures 80-65 ohms, depending on how long I let the voltage die away after having the ignition on.  It stabilizes long term at about 65 ohms, which is okay since there are other circuits in parallel.
Relay primary
With the voltmeter floated across the relay coil primary circuit, it is 13.7v with ignition on (coil is energized). When cranking, it drops to about 0 volts across the coil, and rebounds to 13.4 v after cranking. I can also feel the relay click on, with ignition, then off when cranking, and on again when cranking stops.  Interpretation - during cranking, the ECU releases the grounding on Pin 85 allowing both sides to rise up to +V, or the ignition +V drops down to ~0 v to match what the ECU is commanding.  Is ECU releasing, or switched ignition +V is dropping? [later note - actually, the pin 86 +v ignition voltage was dropping away because the real ASD relay was cutting out.]
Relay contacts
The hot side of the relay contacts stays at permanent +V no matter if the key is in the car, or ignition is on, or off, or if cranking or not. Connecting the voltmeter across the relay contacts, shows that the voltage across the relay always hovers about 0 volts, bouncing around a little bit.  That's strange since I would expect the output to not hang around +V when the relay is open.

Output of relay contact compared to ground is ~ 0v when the car is off, +V when the ignition is on (should be since relay is closed), and t hen ~0 v when cranking.  Strangley, across the relay contacts always hover about 0 volts, cranking or not.  Since Pin 30 is confirmed fuse 6 +V, this means the output side of the relay must float up to about +V even when the relay is not closed. [later note - the output was a floating wire connected to nothing; voltage reading was meaningless and I should have noticed that by the floating around behavior.  Using an oscilloscope would have shown random voltages on the unconnected wire.]

Checking the relay out of the car, with the car battery across the coil, gives a solid click and release.  Resistance goes from infinite down to less than an ohm.  Interpretation?  Relay is fine.

Summarizing three states:
power off ignition on cranking Description
pin 86 ignition +V power available 0 12v 1v This is capable of sparking and heating small jumper cables - be careful what you let this touch, especially pin 85!
pin 85 ECU grounding relay energize not measured not measured not measured I don't know, but I'm betting there is a transistor inside the ECU with a transistor collector terminal pulling this to ground when appropriate.
across 85-86 coil 0 13.5 v 0 v.  ECU commands relay closed with ignition. Commands open when cranking.
pin 30 contacts input 12v 12 v 10 v.  Slight loading, but otherwise stable power.
pin 87 contacts output 0 12 v ~0 Feeds downstream circuits with +12v power when the ignition is turned on.
across 30-87 0 ~0 ~0 Consistently measured ~0 volts [later found output wire was floating unconnected to anything]


Other observations. Maybe a tan wire from pin 87 output goes to fuel injector?  Checked with ohmeter.  No.  Fuel injectors have about 3 ohm across coil.  Top two pins and bottom two pins of 4-pin connector.

Why does ECU command ASD relay open when cranking?  OR, why does switched ignition power die?  Is this about the crank case indicator not giving a pulse when trying to start?  Chilton manual shows crank reference signal error diagnostic codes for years 1996-1998, but nothing for 1993-1995 vans, and nothing about crank signal for 1989-1992 vans (mine).

Check this and confirm crank sensor is giving a good signal.  Otherwise ECU cuts out the ASD relay.
 

Saturday (1 week 6 days):

Salvage yard shopping trip with a friend (thanks Kevin!).  I came home with replacement computer, replacement distributor wires, replacement oxygen sensor, replacement fuel injectors.  I should have grabbed the coil, too.  In case your local salvage yard does not have the appropriate vehicle, you can also purchase new SMEC computers from Mopar.  Looks like my 8-cylinder 5.2L 3-speed vehicle uses part R4379887, 4-speed uses R4379889 for FEDeral state-side vans.  (Okay, side question:  If I have 3 spd plus and O/D overdrive switch, does that mean mine is a 4-speed?)  The one I actually found at the junk yard came from a 1988.  I'm not an engine expert, but considering it had a 6-cylinder, it must have been a 3.9L LA V6.  That would be SMEC or SBEC part R4379929 for FEDeral or CANadian vehicles.

sbec-pinout-schematic

Sunday (2 weeks):

Replacement computer didn't change anything.  Relay output still stays high with ignition, drops low during cranking. Error code 42.  

Monday (2 weeks 1 day):

ASD relay under the dash still works fine.  Actually, I found another relay forward of the firewall on the end of a dangling wire bundle that has the same electrical connection with the middle pin 87A (NC Normally Open) tab in place.  Not sure what this relay is for, but regardless of the part number, it looks like it could be used for an ASD relay.

Is there a ballast resistor circuit that needs attention?  Actually, it would be the parallel circuit that needs attention.  The ballast resistor circuit is used when the car is not cranking.  It provides power to (or indirectly to) the ignition coil.  This is to limit the current flow so the ignition coil doesn't burn up.  However, when cranking, the starter pulls the battery so low, that the ignition coil needs direct power on the (+) side. If the parallel non-ballast resistor circuit is open, then I would get the behavior I am experiencing.

Rooting around, I see two wires on the starter, one big and one little.  Follow them up, and I find the little one is a brown wire that goes to a connector, joined with a little red wire direct from the battery. Other side of the connector is a brown and pink wire, just like the the two colors on the ASD relay.  Maybe?   No... no continuity.

However, I did find two wires under the dashboard labeled "ignition +v" and "battery +v" with single wire connectors.  Looks like you can plug one or the other into the red wire (and 20 A in-line fuse).  Turns out this is what feeds all the interior lights for the custom van.  At least I've learned something today!

The brown and pink wire disappear into a wiring bundle, and from there I have no clue where they go.  How exactly does one "trace the circuit" without knowledge of where it's suppose to go?

I need a working van to start making comparisons to.  Or, I'm about ready to assume it's a fault on the ignition of the ASD relay that is dropping the ASD relay, and hotwire +12v onto the Z1 circuit relay output and hope that nothing blows up.
At this point, thank you to friend Neil who sent an email summarizing with essentially this thought: "When it really starts looking complicated, it's amazing how often it really is a simple thing that has been overlooked."  How Prophetic.

I couldn't sit still and do computer work.  I went outside and after confirming things were still responding as previously, I turned on the ignition.  ASD relay output was +12v.  Then I cranked the engine and ASD relay output dropped to no voltage. Then I did something differently, while monitoring the current flow with a 10 AMP meter, I hooked a jumper wire across the relay so that it didn't matter what the relay was doing.  I decided to force +12v onto the Z1 circuitry while cranking the engine.  Initially a quick tap to see if there would be a spark.  Nothing.  Longer, and feel for heat in the jumper wire.  Nothing.  Nothing on the meter.   No change.  No current draw.  Switched down to a 300 milliamp fused scale on my meter.  Still nothing!  There was NOTHING taking current through the relay.

This confused me enough that suddenly realized I had never determined where the relay output went to.  I needed to know. Because if it fed the ignition coil, there is NO REASON for the ignition coil to be at zero volts if I was shorting +12v to it.  Instead, if there was a short or something, then the whole ignition coil should have burned up. Something wasn't right.

Short story?  After tearing into the dash, I found the ASD relay I found fed the wire labeled "ignition +v" wire I had found earlier in the day.  Since my custom interior lights were hooked to the "battery +v" line (so I can run lights while camping with the engine off), there was literally nothing hooked to the output of the relay.  Uhh... very clearly, the ASD relay I had found and been diddling with for a week was not the ASD relay!

Now that I knew what an ASD relay looked at, I went back with vengeance to find it.  Turns out tucked up next to the brake system on the firewall, there was a little box hooked to nothing, hanging on a metal bracket.  Dangling near the bracket was a terminated wire bundle, but when I looked closely, it was not terminated with tape and a plastic plug like other terminate wire bundles.  There was a little plastic box connected to it.  I unplugged in and VIOLA!!  the plugs looked and were labelled exactly like an ASD relay.  

I poked and prodded with my ohmeter and found that this was a relay, and it clicked fine with voltage on it, but the normally open contacts dropped to only about 4 Mohm resistance when closed.  The connector look copper blue and corroded.  I think dangling down in the engine compartment made this a perfect water run-off connection and water got inside the relay and corroded the contacts.

I took the inside ASD relay from the interior light circuitry and jumper cabled it into position because it physically would not fit onto the cable connector.  Measured volts and everything looked good.  I cranked the engine, and within 1.5 seconds, the old Chevy 318 came to life!  Boy was it good to watch the fuel injectors popping fuel into the throttle body.  It was still running on the junk-yard 6-cylinder computer.

I ran to the junk yard with my toolkit and pulled two ASD relays from a similar van - a 1990 Dodge full-size van with the same engine. I also grabbed two headlights.  From the 1988 Doge Ram Van with the smaller 3.9 L engine mentioned earlier, I took a few spark plug wires, and the ignition coil.  $10.  I almost got the air conditioning compressor out to replace my broken one but one bolt was rusted up badly.  I need my long arm socket.  I guess that's for another day...

Tuesday (2 weeks 1 day):

Now that my eyes were familar with what to look for, one of the little boxes bolted to the firewall started looking like a relay.  And... the wiring harness I found would perfectly reach it. I unbolted the firewall device, and looking at the bottom.. sure enough it was an ASD relay.  I tested it with my meters and it behaved perfectly.

Instead of using one of my new relays, I plugged the wiring harness into the relay that had been bolted unused to the firewall the entire time.  Result?  The van ran beatifully!

I pulled out the 6-cylinder 1988 ECU and repaired the one stripped mounting bolt hole.  I put my original ECU back into the van. I taped up wiring bundles, tucking some behind the battery away from water dripping, and plugged the ASD harness into the firewall mounted ASD relay that had been there all along.

Summary?  Someone had unconnected the harness from the factory ASD, plugged in another one, and let it dangle in the water.  I fixed the van by plugging the harness back into the factory mounted relay.  Both.  What a trip!

Epilogue:

Hopefully our "Big Blue" van has a few more trips in him.  We're anxious to spend a night out at the soaring club field now that Spring is coming on. I now have a small plastic storage bin under the back seat.  Spare injectors. Spare fuses.  Spare coil. Spare relays.  I should go pull the distributor sensing coil, maybe the entire distributor stem going into the engine. 

© 2010 Brian Mork. Please contact me using the copyright link prior to commercial use, or reproducing for distribution in a commercial context.

FOR SALE:  One live-tested fully working ECU PCM SBEC SMEC computer for a 1988 to 1989 Dodge van 6-cylinder or 8-cylinder van,  $65.