95 Suburban K1500 dies & won't start - ChevyTech

[Dapapadon]

I could use a little (lot) of help on my Suburban. ChevyTech, if you read this please help! 1995 K1500 Suburban with 5.7 V8, automatic w/ 121,000 miles.

I bought this Suburban about 2 years ago. It was an auction wreck & I replaced the front sheet metal & radiator. Only 1 fender is original. The truck always started & ran with no problems. Then last spring I was heading out to go shooting and the truck dies about 3 miles up the mountain road. No tools so I backed it down the forestry road to the main road & called a tow truck. Ever tried backing a Suburban down a tight road w/o the engine running? Not fun. Neither was the $300 tow bill.

As soon as we unload it & the tow truck leaves I try it & it fires right up. I put it in the shop with the local guy I use. He has it 2 months & finally gets it to not start. He replaced the Ignition Control Module.

I start driving the truck again and 4 weeks later it dies as I pull around to back up and leave work. Same thing, will not start for anything. So I get a co-worked to push me into a parking spot with a forklift. Two days later my son & I go get the truck, it fires right up & drives home fine.

I leave it parked for several months then replace the fuel pump. I took a guess at the problem, it was the original pump so I figure it needed replacing. It fires right up after replacing the pump, AC Delco pump from Rockauto.

By this time the tags have expired so I get a trip permit so I can drive it around and I need to go to DEQ for a smog test. I drive it around the neiborhood some then on the third day I figure I'll drive to work on my day off. I stop at a local store on the way. As I'm leaving there and pulling onto the main road it dies again. Same old thing, cranks but will not start. Napa is a block away so I get a can of starting fluid and a fuel pump relay. Neither had any affect. Although it did seem like it coughed a litlle once or twice with the starting fluid. Another $125 tow truck ride home. By that time I'm frustrated with the problem & decide to wait for warm weather. Oh yeah, truck doesn't start when i get it home this time.

So now the weather has warmed up. I've been drive my old 70 Chevy C20 all this time and felt the urge to start back on it. So I'm back to the forum and start looking at post from other people having GM TBI problems. Why didn't I think of that last year. Anyway, ChevyTech recommends checking the fuel pressure first on TBI engines so I ordered an Actron GM TBI fuel pressure gauge with adapter and the adapter to replace the fuel filter. The gauge will not fit the filter replacement adapter but the one that came with the gauge did fit behind the filter.

I get 14 psi when I turn the key on and it holds at 14 psi with the engine running. Oh yeah, now it wants to run again. The fuel pressure does drop as soon as I shut the key off. So I'm guessing I have a regulator or injector problem. My son will be home later this evening & I'll watch the injectors as he shuts the engine off.

I need a game plan to find the problem. Could the fuel pressure dropping when I shut the key off be part of the problem? Can I leave the fuel pressure gauge adapter installed until the problem returns? And I'm usually by myself when this happens. But I can get my son there most of the time. Right now I'm not sure if I have a fuel or ignition problem. I need to get together a tool kit to locate the problem. And keep $200 in my wallet in case in need another tow truck ride.

Sorry this got so long.

Don

[95 S_Trucker]

When it dies, does it shut right off or sputter and die?

Did it have spark when it cranked and wouldn't start?

Were the injectors spraying when it cranked and didn't start?

If it has fuel injectors spraying but not any spark, look for a failed ignition module. Was the last module installed correctly with heatsinc compound?

If you don't have spark or fuel injectors spraying, look for a faulty pick up in the distributor. Is there any play in the distributor shaft? Can you see any marks on the pick up where they have contacted each other? If there is, replace the distributor.

Besides the fuel pump failing, those 2 components are the most common on letting tbi trucks sit.

[ChevyTech]

Don't keep replacing parts hoping it will fix it. The quality of replacement parts is so bad that new parts may cause more problems. Even AC Delco parts can't be trusted anymore. It seems parts sold as AC Delco now come from a variety of sources and are sometime very poor quality. Delphi is a manufacturer I still trust.

The problem you are having sure sounds like a bad module in the distributor. Many of the replacement modules are failing within the first 200 miles. Like 95 S_Trucker asked, did you put heat sink compound under the new module when you replaced it? Without the compound the module will fail.

Don't worry about the fuel pressure dropping as soon as you turn the key off. Some TBI units had a hole in them that bleeds off the pressure as soon as the pump stops, and I have never been able to determine which TBI unit had the holes, without taking them apart.

Next time it does not start you need to do some testing so you are not guessing on what the problems is.

95 S_Trucker gave good advice.
When it won't start:
See if the injectors spray fuel.
See if it has spark

Both the injectors spraying and spark are dependent on the distributor module, to function. The computer will not trigger the injectors without a reference pulse from the distributor module.

You should also test to see if there is power to the red wire and the white wire to the injectors with the key on when it will not start. Test with one probe on a good ground when you do this test. DON”T test between the two wire to the injectors.

Here are a few things you can try with it running to see if it make it die.
Wiggle / move around the wiring that goes to the TBI unit about 6 inches away from the TBI unit to see if the wiring is breaking. A common breaking point is right next to the TBI grommet.

You can unplug the fuel pump relay with it running and it should keep running. There is a redundant circuit through the oil pressure sensor. If the engine dies when you unplug the fuel pump relay, then you need to replace the oil sensor by the distributor. But ask us about the brass elbow that may break first.

With it running take your hand and give the computer a light slap and see if the engine dies. Don't get to rough with it. Wiggle the harness right by the computer.

I would also try moving wiring harnesses wherever it is easy to reach them and move them a little.

Make sure the battery connections and grounds feel tight.

[Cabnchassis]

ChevyTech is dead on about replacement parts. The only thing I'd add is don't use any bosch parts at all. These trucks can't tolerate them for some reason.

[Mr_Rich]

You guys are right on about the parts situation. I've managed to keep my truck running through parts I've saved/ accumulated over the years. I thought it was time for a new dist. cap and I've always used Accel (Made in Canada, I might add) with the brass contacts and never had a problem. I recently purchased an Accel dist. cap which is now made in China. After getting frustrated with fitment issues I gave up and cleaned the old Made in Canada dist. cap and re-installed it in seconds. I'm wondering what brands I can still find Made in USA, Canada, or even Mexico (?).

[Dapapadon]

Thanks for the fast replies! I'm an old school carb guy I guess. I usually take this new stuff to a shop but that didn't work on this interm. problem.

I'm by myself when the problem occurs. And wasn't really sure what to check. I think I can get someone to crank it for me next time so I can do some checks.

I didn't replace the ICM, a local shop did. So I'm not sure if they used heat sink compound or not. When i had the disrtib. cap off to check the pickup coil there does appear to be white grease squeezed out from under it. It is a Delphi unit.

The distributor shaft doesn't seem to have excessive side play. Maybe 0.002" at most. I can't tell about the pickup coil. I used a flashlight but can't get a good look at it. There is like a round brown coil over the trigger on the disrtib. shaft. I couldn't see any damage or rub marks.

I wiggled the wiring around the TB and it stayed running no problems there. I had to look up where the computer is but didn't get it to die while wiggling the wires there or tapping on the computer.

It did die a few seconds after I removed the fuel pump relay. I verified this 3 times and each time it died in a few seconds. Where is the best place to get the oil pressure sensor? Looks hard to get to with the distributor in the way.

I have a meter I can keep in the truck to check the red & white wires on the TB next time it will not start.

The truck runs fine (when it runs). I want to say I had the local mechanic shop do a tuneup last time I had problems but that was almost a year ago. I do see some corrosion on the cap & rotor and think I will replace those. May do plugs as well.

Again thanks for the quick replies.

Now it's off to work I go.

Don

[ChevyTech]

Originally Posted by Dapapadon

It did die a few seconds after I removed the fuel pump relay. I verified this 3 times and each time it died in a few seconds. Where is the best place to get the oil pressure sensor? Looks hard to get to with the distributor in the way.

The oil sensor is a common failure part.

I always use OEM, but they are not great either because we see plenty of them fail.

It is very easy to break off the brass elbow that the sensor screws into. Support the elbow real well when you try to loosen the oil sensor. Yes the distributor is in the way. Often after people break off the elbow, then they remove the distributor to make it easier to get the broken piece out of the block. Some people remove the distributor for better access so they can support the elbow better.

A member on another board just told me the dealer told him the elbow is no longer and “available“ part, but some dealers still show having some in stock.

The white paste squeezing out of the edges distributor module is a good sign. All the heat sink paste I have seen is white. Delphi module too! Great!

[Dapapadon]

I've started the truck several times since my last post w/o problems. Sunday I left it running while I mowed the front yard, about 20 minutes.

Today I picked up an oil pressure sensor from the Chevy dealer, $66.83 (ouch). And a cap & rotor button from NAPA.

I started it this evening & it ran for 15 -20 seconds then died & would not start. I think that is the first time I was happy about a vehicle not starting. Anyway I started checking. I still have 14 psi fuel pressure, but no spark & the injectors are not spraying.

ChevyTech, my wires going to the injectors are dark blue, pink, light blue & pink w/ maybe a tracer. But no red & white. Are these the right wires?

So does this sound like the ICM again? if so, Rockauto list several ICMs, a Delphi #DS10059 & 4 different AC Delco units.

Sorry it took me so long to post again. I just don't get much done on days I work, then I slept most of yesterday. Don

[95 S_Trucker]

Nope. It sounds like a pick up problem in the distributor.

If it were just the wires at the throttle body, you would still have spark. If it was the ignition control module, you would still have the fuel injectors spraying.

If it were my truck, I would be replacing the distributor.

[Greenlee]

I had an annoying problem like this, but mine would usually start right back up after it died (89' TBI). Took it to a local shop and they didn't seem to know any more than I did. I felt like I was just throwing parts at it.

The last part I threw at it was a new coil. It has been about a year now and that seems to have fixed it. If that didn't work my next step was going to be replacing the entire distributor.

It might be worth a shot to change your coil. I was getting a lot of the same advice you are getting here on the forum. The coil was relatively cheap and easy to replace (electrical doodad right in front of the distributor).

[95 S_Trucker]

If the coil was the problem, it would still have the fuel injectors spraying.

[ChevyTech]

Originally Posted by 95 S_Trucker

If the coil was the problem, it would still have the fuel injectors spraying.

Yes, Trucker is correct.
If the problem was a bad ignition coil the injectors should still be spraying fuel.

It could be a bad pickup coil. Test it.
Pickup coil testing:
500 to 1500 ohms between terminals.
Infinite from one terminal to ground.

When testing the pick-up coil resistance, the key should be off, and the pickup coil should be unplugged from the distributor module.

See if the distributor shaft will wiggle sideways.
On these distributors the housing/upper bushing area can get so worn out that the shaft will move sideways so far that the points on the pickup coil pole piece get hit by the reluctor points on the shaft. When this happens the ECM receives compromised signal for RPM and timing issues.

If there is oil coming up the shaft and getting out onto the pickup coil – replace the distributor.

These distributors can also have problems because of loss of magnetism needed for the pickup coil to work.
If the magnetic material on the shaft in the reluctor wheel area is cracked into pieces replace the shaft or the whole distributor.
Here is a thread with a photo showing the magnetic material cracked.
http://www.chevytalk.org/fusionbb/sh...e0b728a96e45b/

[Dapapadon]

Had to work a long shift Sat. and that threw me off for Sunday as well. Monday the rain started. Sorry I'm so slow on this. And thanks for the help.

I tested the coil today and have 482 ohms across the coil. But I have 16 mega ohms to ground.

NAPA can me a Delphi part in the morning. Now how do I remove & install it?

Don

[Dapapadon]

NAPA called back later saying they needed to order the out of CA. I stopped by today & paid for it. Should be here middle of next week.

Don

[Dapapadon]

Update - The coil came in Tuesday & I picked it up on my way to work. Wednesday I pulled the distributor and installed the coil at work. The coil was bad. There was flacky light brown stuff when I pulled the distr. main shaft. It looked like pine tree pollen. The outside of the coil insulation was missing exposing the copper coil.

I had bought dielectric grease which I figured out was wrong for the module. It took several phone calls but I found the heat sink compound and reinstalled module, then the distributor. Correction, that was after I installed the oil pressure sensor.

I hooked everything up & tried it. It fired once but would not start. Checked & didn't have fuel at the injectors or spark. I pulled the cap back off & checked the coil, ok.

There is what I think is called a shield over the coil & reluctor. I turned that counter-clockwise then put it back together. To my surprise it fired right up. I think my timing is a little off & I need to set that. From what I've found online there is a connector behind the glove box I need to disconnect before I set the timing. Is that correct?

Also where should the shield over the pickup coil & reluctor be set?

I'll do the oil pressure sensor check of pulling the fuel pump relay when I set the timing.

Thanks for the help on this! I may get to go shooting soon!

Don

[95 S_Trucker]

The timing connector is on a light brown wire. there is a large wire harness running vertical under the glove box. That wire is outside of the harness.

Get the truck to normal operating temp. Unplug the connecter. Set timing to 0 degrees. Shut off engine. Plug in connector.

Was there any play in the distributor shaft? If there was, your new pick up coil will live a short life.

[95 S_Trucker]

Here you can see where the timing connector is on a 95. I have the dash out of one today:

[Dapapadon]

Agian, no start.......

The bushings in the distributor housing are good. When I was putting it back together I put a little oil on the shaft. As I started to install it the top bushing was "skinning" the oil off the shaft. So I pulled it out, cleaned up a small amount oil at the bushing, wiped the shaft clean & reinstalled it.

If I did it right here is a picture of the old coil, no damage on the inside only on the outside.

The shield over the coil looks similar to the second photo.

I started the truck severals times yesterday with no problems. Today I started it a few times then went to a meeting at work. On my way home I picked up a distributor wrench to tighten the hold down after setting the timing.

Got home & the truck started several times. Then I let it warm up, I disconnected the connector behind the glove box, set the timing, tightened the hold down, verified timing and shut the truck off. I reconnected the timing wire, started the truck, pulled the fuel pump relay & the truck stayed running. So I put the tools away.

Went back out 10 minutes later and it would not start. And still will not start. By the voltage gauge the battery is getting a little low, but it cranks just fine. I'll put the charger on it tonight.

My son had already left for work when it decided to not start so I have no one to crank it for me. But I assume I'm back to no fuel from the injectors and no spark but I will confirm that tomorrow.

Don

[ChevyTech]

The wire terminals in the connector that plugs onto the distributor module can get stretched out making loose connections. This can cause intermittent stalling, a no start condition, or code 42 problems.

The comments you made about moving the sheild over the pickup coil makes me think you could have moved the wiring enough to make connection when you went back in and moved the shield.

These distributors can also have problems because of loss of magnetism needed for the pickup coil to work.
If the magnetic material on the shaft in the reluctor wheel area is cracked into pieces replace the shaft.

Photo of cracked magnet in this thread:
http://www.chevytalk.org/fusionbb/sh...e0b728a96e45b/

The condition of the magnetic material is more important the slower the the engine is turning. A low battery will exaggerate bad magnetic material on the distributor shaft.

[Dapapadon]

Sorry guys, you are giving me good advice. I should reply with better details.

When I had the distributor apart I could see no damage of the magnetic piece on the distributor shaft. The truck was cranking fine yesterday. The voltage looked low on the dash gauge so I put the charger on it overnight.

I confirmed no fuel from the injectors & no spark today. I had my son crank the truck while I wiggled the connectors to the module. It did not even try to fire.

After the initial problem the local shop had the truck 2 months before they could get it to fail to start. They replaced the ICM and it ran flawlessly for 4 weeks then it stalled at work & wouldn't start. I've let it set for several months twice, once before I replaced the fuel pump and again after that. Could the ICM be bad again?

The 2 wire connector to the ICM would be easy to replace. It goes from the coil to the ICM & I could take it off to replace. But I'm reluctant to cut the original wiring harnes to replace the 4 wire connector.

Guess what I'm saying is I'd feel better replacing that 4 wire connector if I had a known good ICM.

Don

[ChevyTech]

Originally Posted by Dapapadon

Could the ICM be bad again?

Yes!

The quality of replacement parts is terrible.

It seems like just about every brand is cutting corners, and many parts are now made in China.

Many replacement distributor modules are failing in the first two hundred miles.

Make sure you used heat sink compound under the new module. Without it they fail fast.

[Dapapadon]

I ordered a Delphi ICM after ChevyTech's reply. It came in last Friday. I also picked up plugs & plug wires in the mean time. Today I had time and installed everything. The truck fired right up afterwards. It would not start the few times I tried after my last post. I did not try it before I started today.

I'll order a spare ICM just in case. I plan to start it several times a day for the next week or so. I need to get a trip permit from the DMV so I can run it through DEQ, our version of a smog check. I already got 1 trip permit in Jan. and we can only get 2 per calender year. So I need to make sure everything is ok.

I did put heatsink compound on the ICM before I installed it and I did clean the distributor base where it mounts. Those 4 position plug wire seperators are a pain to open.

It does have a stumble or miss if I hold the RPMs in the 1000 to 1300 range that I don't remember it having before. I'll double check the plug wires.

Don

[68c10airstream]

Originally Posted by Dapapadon

I ordered a Delphi ICM after ChevyTech's reply. It came in last Friday. I also picked up plugs & plug wires in the mean time. Today I had time and installed everything. The truck fired right up afterwards. It would not start the few times I tried after my last post. I did not try it before I started today.

I'll order a spare ICM just in case. I plan to start it several times a day for the next week or so. I need to get a trip permit from the DMV so I can run it through DEQ, our version of a smog check. I already got 1 trip permit in Jan. and we can only get 2 per calender year. So I need to make sure everything is ok.

I did put heatsink compound on the ICM before I installed it and I did clean the distributor base where it mounts. Those 4 position plug wire seperators are a pain to open.

It does have a stumble or miss if I hold the RPMs in the 1000 to 1300 range that I don't remember it having before. I'll double check the plug wires.

Don

Don, If you are savy with a voltmeter double check the distributor for a poor ground

Here is the procedure; start up truck, scratch a shiny spot onto the distributor neck, touch a voltmeter lead on the negative terminal of the battery and touch the other voltmeter lead on the shiny spot on the distributor neck

Good reading should be .2 volts (200 millivolts) or less. Anotherwords if the voltmeter reads more than this the voltmeter is starting to supply the needed ground!

[68c10airstream]

I meant to add that your truck will not have spark or injector spray without this ground being good.

Remove the hold down clamp, remove the hold down bolt, clean all corrosion off and clean the intake and especially clean the base of the distributor where the hold down rest on.

As a past GMC dealer mechanic fixed many trouble code 42 (est bypass) by fixing a poor ground, never installed a part, just performed the procedure stated above

Trouble code 42 typically came about after a tune up or engine replacement because the distributor was moved to a new spot that is corroded, and the voltage drop caused this. Leaving in the salty north sure causes it share of troubles!

[Dapapadon]

Thanks for the reply. I'll give that a try tomorrow & report back. Heading out to work shortly.

Don