1995 Chev C3500 - Stalling + No Start Condition -- FIXED ?

[vinnieg]

Naturally we can't get this truck to stall, die, or fail to start when we have rotation. When the truck was last in we did find corroded wiring to the PCM and the fuel solenoid and repaired those. The problems with the wiring were discovered while going over the wiring to diagnose a starter problem and were fixed when found. Since the engine never failed to start after we thought the starter issue was repaired we sort of presumed the stalling issue was resolved as a byproduct. BTW, there were no codes at all when we initially scanned the truck nor did we have any the whole time the truck was in the shop.

Not so. The truck ran good for a few days then stalled and would not restart. The driver called the shop and told me what happened and then said it was doing the same thing as before. When I asked about starter engagement and engine rotation he first said the engine was not 'turning over'. Since he was on his cell phone I had him try to start the truck so I could hear what was going on. (I know, we hate it when customers do that to us but I really needed to know if the engine was rotating or not.)

He hit the starter and the engine cranked and cranked and cranked... I had to yell at him to let go of the key. He repeated the attempt several times and each time the engine rotated but failed to fire off. That was about two weeks ago and he has called back a couple of other times and we went through the same steps and each time I told him it needed to come in so we could diagnose the problem.

They brought the truck in today and this time it has a DTC 35 "Injection Pulse Width Error (Response Time Short)". Right now we are leaning toward either a defective fuel solenoid or PCM. Hopefully we can narrow it down further tomorrow. Has anyone else run into this particular problem? If so have you any advice? Also, if a PCM does it have to be programmed to the vehicle by the dealer. According to what we are reading from the Modis it looks like a trip to the dealer is required but other information (Mitchell & AllData) it isn't so clear.

Thanks,

Max

[steven kiser]

the pcm will need to be programmed. if you have a tech 2 you can do it. look at injector module. as said in other post these are prone to failure and will cause issues like you mentioned. MAKE SURE RESISTOR IS CORRECT.

[vinnieg]

Steve,

Thanks for the response. As the shop manager I'll have to get the tech to point out everything for me but I think you are on to something.

We don't have a Tech 2 (just the Modus), but might be able to borrow one from a nearby shop. If the injector module you are referring to is the one mounted on the front lower center of the intake manifold that is one we are looking at hard.

The tech isn't in yet but I am curious about which resistor you are referring to. I don't recall the tech mentioning any resistors so it might be something that was overlooked.

Thanks,

Max

[steven kiser]

if you look inside the module where the plug connects there should be a resistor inside there. it slides along the spades and rests on the bottom of the plug receptacle. if you look inside you'll see it. if you don't see something in there and just the black bottom of the plug housing then it's missing. if it's missing you'll get a vary of failure issues. you just can't replace it with a resistor. there are a few different resistors. i had one in a few years ago without the resistor and if i remember correctly there was a tedious process of selection. close will not solve the problem. i think the resistor is measured against the pump not the module.

[vinnieg]

Steve,

Looks like you are onto something good. Just went over things with the tech and there are two modules on this truck. One is the original unit which apparently failed some years back. The second is installed up off the engine with a heat sink and is the one that seems to be failing now. We were never able to get the truck to stall here at the shop and while visiting another shop that works on lots of diesels a couple of hours ago the owner asked if we were testing with the hood open or closed.

Man it is hard to keep a straight face when someone asks a question like that, (I have asked other techs that very same question a few hundred times). He recommended closing the hood and putting a drop light in there as close as possible to the module then if it fails hit it with some "cold shot" and if it will start immediately without waiting an hour or so the module is the problem.

Tech confirmed the resistor is installed correctly and making good contact so now all we have to do is wait for it to stall....

Thanks for the help, hopefully the problem can be fixed today and I can have the bay back. You know, just in case any customers show up, I mean the politicians said things are better didn't they?

Max

[steven kiser]

i use a heat gun to bring the module temp up. another thing i've run across in these is air in the fuel. i take a piece of clear tubing (lowes) and remove bleeder hose from injector head, splice a piece of clear onto it and connect the other end to the head. run the truck and watch for air bubbles. if you see any replace the rubber fuel lines from the tank. i've had both electronic as well as fuel issues in these. leaks in the lines are very difficult to locate so i've found it prudent to replace all. if there is a hole in a steel line it will show a leak. porous rubber line may not, it will suck air but may not leak fuel. another point here is as a rule (at least in my shop) once the module is relocated and a cooling plate installed the failure rate drops to almost zero. i've replaced a few but usually because of physical damage. IF you decide to replace the module and you didn't replace the original let me make a suggestion. use a light and mirror to get the #'s off the original module, check against replacement. the replacement may have been updated so if the #'s aren't the same call the dealer and see if the old crosses to the new. if they are different and the replaced unit doesn't cross to the original you may have an issue that needs investigation. whew, what a mouth full here. o.k, if this is the case what to do. i first look into the old module and see if the resistor is still in it. if yes the i order from that #, remove resistor and install into the replacement (one i'm installing) and install it on the cooling plate. if no, then i ask the customer how long the replacement one has been there and if there have been any and i mean any issues with the engine. long cranks etc this may have been an issue from the get go but not to this extent. you're in a position here where you may be trying to cover dog **** with gravy. inadvertently of course, because someone else improperly repaired it the first time. you may have to correct the original botched repair. i've seen this before and the first time it happened i banged my head for a while. now on the rare occasion i see one of these, the old module is still on the head, and i have a driveability issue i check the #'s. it's saved me a few times. not all shops operate at a quality level............

[vinnieg]

Well, Friday evening late, after running the truck for a long time with out stalling the tech did another tap & wriggle test. This time when he tapped the on the Fuel Driver Solenoid pigtail the truck died instantly. Previous tap tests didn't show this but perhaps the extra heat caused it to show up this time. Even after a cool down period he was able to duplicate the problem so it looks like a new FSD is going to be in order. We will retest this morning and hopefully get this one cleared out soon.

[vinnieg]

UPDATE: Dateline WPB, Florida

The saga continues but things are beginning to look up finally. After stopping and reterning to Step 1 several times we were able to duplicate the Stalling/No Start condition. Interestingly enough we experienced more than one type of failure which sort of made troubleshooting more of a problem. Seems the 'stories' we received from two different drivers, the owner, and his wife all differed slightly and because they were all focusing on the starter.

Once we were able to heat the FDS enough it would fail a tap test. In fact using about the same pressure it takes to tap the keys on a touchtone telephone the engine would DIE! No stumble, no hesitation but absolute and instant death. That pretty much convinced me the FDS had to be replaced. Bought a new one from GM, installed, and ran it over and over. Tap tested and even carried the tap test to new dynamic levels, (smacked it pretty hard), and no failures.

Lesson learn on this and other vehicles: Do not call it fixed just yet. I told the customer that we would continue testing to confirm this was indeed the fix. An hour later the truck stalled and when it restarted might run for 5 - 10 seconds then stumble and die. Hmmmm, didn't stumble before when we killed it tapping on the FDS but now it stumbles like it was running out of fuel.

Step one all over again. No codes stored this time. No errors noted in the data stream. More research (Mitchell, AllData, Web searches, several forums, numerous phone calls to other shops, etc.) and had suggestings ranging from fuel pumps to cosmic misalignment of the stars. Let the truck sit and cool down for an hour with the hood open and it would restart and run fine. Close the hood, let it run for an hour or so and once in a while it would stall out and die. Other times it continued to run fine. Shut the truck off and let it sit for 20 minutes and suddenly it went into the 5 - 10 second run or long crank without starting condition.

Digging deeper we checked the fuel pumps and found the lift pump not turning. Checked voltage and had good voltage and ground was good. But the tech data said it would not run if the lift pump was inoperative. Okay, maybe it is intermittent? If that is the case maybe it is losing the signal from the oil pressure sending uunit and shutting down. Nope, signal good but failure was rare so maybe we just weren't catching it. Finally in desparaqtion we unplugged the fuel pump and the oil pressure sending unit and the truck ran just fine. Took several hours and attempts but finally we were able to duplicate the failure. Pulled the frome mounted fuel pump and tested it on the bench. Could not make the pump work even after 'dynamic inspiration'.

We are halfway through the second full day of testing since on repeated failures or multiple failures it s my policy to retested to failure or until we are sure there isn't yet another defective component or bad wire that can sneak in and bite our a**. If all goes well I'll take it out this afternoon for a 50 mile test drive and try to make it break down.; If all goes well we'll test it again to morrow and call the customer and tell him to bring money.

If anyone knows of anything I may have overlooked please don't hesitate to say so since I really don't want to see this truck again until he needs an oil change.

Thanks,

Max

[vinnieg]

Well, it has been about 10 days now since the truck left the shop. No phone calls, (we check them regularly for a dial tone since they aren't ringing much lately anyway), and no other indications of failure. (Almost hate to mention it since that sometimes jinxes what was otherwise a sucess story.)

I want to thank everyone for their ideas and suggestions.

This was one of those things where the customer has had problems for several years and apparently everyone was simply treating whatever 'first sympom' they came across and calling it fixed. Instead the truck suffered from an accumulation of problems which were intermittent and as we all know things like that tend to work when it is in the bay and will fail for the customer at the worst possible time.

Starter problems were the result of insufficient clearance between the starter pinion and the flywheel ring gear. The stalling issue appears to have been the result of an intermittently failing FDS. The hard starting issue appears to have been caused by a defective fuel lift pump. Take those and add 4 different drivers, failures happening in a random manner and you can see the mathmatical permutations are pretty extensive. Experience one problem and one problem only = Fairly simple to track down. Combine several problems in random order with several differnt drivers under differing conditions = Nightmare.

I stress pushing and testing to failure no matter what the customer complaint is and if they tell you it is intermittent a 10 minute diagnosis ain't gonna make things any better. Shooting from the hip with guessinositcs ain't gonna cut the mustard either. Ya gott keep pushing, driving, testing, etc., until it does to you what it does to the customer. Then take each occurance, start with step A and troubleshoot until you find a hard failure. After that go back and hammer it again until it fails again. Then go all the way back to step A, disregard what you did before just in case the part was bad or you made a mistake. Find and fix the second problem. Lather up, rinse, repeat as necessary.

I hate to guess how many hours we put into that damn truck but at least it is working, the customer is happy, and the mechanic is ready for the next one knowing that what he learned on this one will make the next one easier. Hopefully.


A couple of valuable lessons we learned on this truck:
1 - Close the hood while you are testing something that may be heat related. Duhhhh...
2 - Measure all things mechanical that have a long historuy of problems, (Starter issues), and find other similar vehicles and measure them for comparison.
3 - Listen to ideas from other shops and try them out even if they seem far fetched. (If what you are trying ain't soving the problems maybe their ideas aren't any sillier than your own.)
4 - It is okay to roll your eyes and make faces when the shop manager wants to try something unorthodox. After all he is gonna take the heat if it don't work.

A big thanks to everyone who chimed in.

Max

[steven kiser]

thanks for keeping us posted. lets hope.