'95 Jimmy no start - follow up

A couple of weeks ago I posted a question about 1995 Jimmy with no-start issues. Here we are now, and still having problems.

I have replaced or had replaced:

-- Fuel pump
-- Relays
-- Wiring around the fuel pump and relays
-- Ignition switch
-- Battery
-- CPI injector

None of these have made any difference whatsoever.

The Jimmy will start and run fine about 75% of the time. The rest of the time, it will crank, but the fuel pump is very obviously not running and the truck won't start. You can try to crank it all day long and it won't start, however, if you leave it sit for 10 minutes, an hour, sometimes even the next day, it will fire right up on the first try.

When it does start, there are no other issues -- idle is perfect, and it runs fine. Sometimes it will go weeks without any starting problems, and then just starting acting up constantly.

I'm at my wit's end. Anyone have any thoughts on what else might be causing the problem? At this point I've sunk quite a chunk of change into completely useless repairs...

Thanks!

-- Robert

Any check engine lights?

Any check engine lights?

Nope. And I've had it hooked up to computers at two different mechanics. Unfortunately, when it's starting, there is nothing there for them to find -- everything diagnoses perfect (and this no-start issue is so inconsistent that it just hasn't acted up when it's been in the shop).

Something, somewhere, is simply causing the fuel pump to not start. It doesn't seem to make any difference if the car has been driven recently, if it's been short drives or long drives, whether it has a full tank or not, what the temperature is -- there just doesn't seem to be common condition that could help figure this out.

And as I've said, just about everything related to the fuel pump has been replaced.

I just really don't get it. I could understand it if it just wouldn't start, but what could make it fail to start, then leave it sit for a while -- without adjusting or touching anything -- and then it would suddenly decide to run the fuel pump? And it's not even like it's a consistent period of time. I've had it fail to start and then fire right up 5 minutes later. Or, like right now, it's been sitting dead in the driveway for the last 3 days.

-- Robert

Check the ignition switch in the steering column.

It is a small black module that is prone to failure.

Check the ignition switch in the steering column.

It is a small black module that is prone to failure.

It's been replaced. In fact, almost all of the parts I mentioned in my first post have been waranteed out and replaced at least TWICE (just in case defective parts were an issue) -- but nothing has touched the symptom.

That's what makes this so frustrating. Likely, there is something simple somewhere that is preventing the fuel pump from consistently running. But I haven't been able to figure it out, and neither has my local mechanic, nor a GM dealership.

And at this point, I can't even get rid of the damn truck for anything more than just scrap, because it doesn't run.

-- Robert

-- Fuel pump
-- Relays
-- Wiring around the fuel pump and relays
-- Ignition switch
-- Battery
-- CPI injector



I was going through receipts and paperwork and discovered that the above list of repairs I posted wasn't quite complete. I've also replaced the crank sensor. Additionally, the Jimmy has been hooked up to a computer several times (as recently as last week) and there are no error codes showing.

-- Robert

Well at this point I doubt if it's spark, so lets go back to fuel. What is your fuel pressure (hook up a tester to the shrader valve on the intake)

When was the last time you changed your fuel filter?

Wonder if you also got a bad fuel pump (not uncommon)

Well at this point I doubt if it's spark, so lets go back to fuel. What is your fuel pressure (hook up a tester to the shrader valve on the intake)

When was the last time you changed your fuel filter?

Wonder if you also got a bad fuel pump (not uncommon)

Unfortunately, I don't have the equipment to test the pressure at home, so I have to rely on the mechanic (at least I can trust them -- they're family-owned). The problem is that when it is starting, it runs fine and all pressure tests come up normal. It sat at the mechanic for 3 weeks at one point -- starting every time. The one time it failed during the first week, they pushed it into a bay that instant, hoping to fix something -- and by then it was starting again, giving them normal readings and starting up every time they tried it for the next 2 weeks. I took it home, it drove fine for a while, and then sure enough, within a couple of weeks it was doing the same thing (that's another thing -- it doesn't have consistent intermittent problems...it will drive perfect for a month or so, then start acting up almost every time I try to start it for a few days, and then it will decide to be fine again -- generally just about the time the mechanic gets it again).

It had a full tune up, with filter replacements not all that long ago, and the mechanic has told me that the filter doesn't need to be replaced yet (it was acting up both before and after the last replacement anyway).

As for the fuel pump, this is the 3rd one in less than a year. That was the first diagnosis of the problem. So it was replaced. When that didn't fix it, we waranteed the part out, assuming it was defective, and put in another new one. I suppose it's *possible* to have 3 bad pumps in a row (2 of them brand new), but unlikely.

It's more like something is just preventing the pump from running every time. I don't know if it's possible that the computer "thinks" it's running the pump when it isn't, or if there's some sensor somewhere that is faulty -- but how do you test these sorts of things when it IS working? I'm rapidly running out of money to just keep replacing things that *might* be the problem...

So far, I've tried everything I and the mechanic can think of, even going so far as to go out of my way to try buying gas at different locations -- just to cover the possibility of some unknown additive in the gas from my "normal" station.

-- Robert

How's yout oil pressure sending unit? That can cause the same symptoms. What happenes is that the ECM gets a false reading from the pressure sender as being to low and won't allow the car to start to protect it. Another thing, when you replaced the CPI unit, did you replace the nutkit as well? (inbound/outbound fuel lines in the upper plenum)

Do you hear the fuel pump relay click when you turn the key every time? A good place to start is to connect a probe light an make sure the pump is getting a continous flow of voltage once the key is turned on. Check and make sure grounds are all good, both at the relay and at the pump. Energize the pump manually when it doesn't start, and see if it starts.

Ok I have a 92 jimmy...Don't know if it the same but this drove me crazy for about a week before I figured it out.

I am poor. So I diagnosied a bad fuel pump...( I should mention that I have been an Electronics Technician for going on 20 years). I droped the tank and pulled the pump. I bench tested it and it was bad for sure.

I replaced it (broke one of the fuel lines in the process...fixed that too) and it fired right up. I nearly broke my arm patting myself on the back.

the next day I went to run a service call and NOTHING...I was pissed I listened for the pump and no noise, all though I could hear the relay click.

I hooked an extra meter to the fuel pump wires to check for voltage getting to the pump...And it started right up!

To make a long story short....I finally found that I did not tighten a ground wire that runs from the top of the tank to the back of the car and is hook to chassis ground just behind the bumper. It was just loose enough to not work sometimes. I took it off, sanded it to clean it up and the spot that it is screwed to. A little locktite and made sure it was "Goodandtight" Its never been a problem again (almost a year ago)

Hope this helps.

Bill

hey when it wont start the next time spray some starting fluid in the throttle body and see if it fires up......if it does then you know its a fuel problem.....if not then you can eliminate fuel as the cause....

To make a long story short....I finally found that I did not tighten a ground wire that runs from the top of the tank to the back of the car and is hook to chassis ground just behind the bumper. It was just loose enough to not work sometimes. I took it off, sanded it to clean it up and the spot that it is screwed to. A little locktite and made sure it was "Goodandtight" Its never been a problem again (almost a year ago)


This sounds worth investigating -- given that so much in the fuel system has been replaced/checked, it seems that about all that remains is some stupid little thing. ;) Can you tell me about where this ground wire is attached behind the bumper -- center, right, left?

To blazes9395: Right now is the longest it's gone without starting (a week now). Normally, it will decide to fire up again before I (or my mechanic) can attach anything for any sort of diagnosis. Now I just need to wait for some of this snow to melt so I can crawl underneath and attach a light...

To soulsurvives: I've tried the starter fluid trick and that *will* get it to fire up -- at least for a few seconds -- but it won't stay running.


Thanks for the tips everyone -- I really appreciate all of the suggestions. Hopefully I (we!) can get this figured out soon.

-- Robert

I have somewhat same problem but mine will start after cranking for a few times when it has been sitting for a few hours...pulled the fuel filter off and turned the key on and no fuel.. cranked it and fuel came , stopped cranking and fuel stopped. if I hit it with starting fluid it fires up and runs great...relay clicks..cant understand mine ..I was told that the fuel pressure switch can cause both our problems but cant seem to locate where it is Do you have an idea where?

Id check the ground on that, seems that might be part of the problem, its bouncing around or ocming in and out of contact.....

Id check the ground on that, seems that might be part of the problem, its bouncing around or ocming in and out of contact.....


TO DETROITMUSCLE..what would cause the pump not to run with key on but run with cranking on 92 jimmy? will eventually start with cranking the hell out of it but took filter off and turned key, no fuel, but when cranked motor over , fuel came shooting out, and stopped when I stopped cranking...could you help me out?

TO DETROITMUSCLE..what would cause the pump not to run with key on but run with cranking on 92 jimmy? will eventually start with cranking the hell out of it but took filter off and turned key, no fuel, but when cranked motor over , fuel came shooting out, and stopped when I stopped cranking...could you help me out?
If the wires havnt been tampered with, start by looking at the relays and go from there.

If the wires havnt been tampered with, start by looking at the relays and go from there.


THE ONE RELAY UNDER THE HOOD DOES CLICK WITH KEY

Hey there is a pulsater that is hooked to the fuel pump inside the tank that can tear and give you this problem.I'll bet that is your problem if the ground wire is hooked up from the aforementioned reply. Let us know.

I found out that if I jump the orange and grey wire going to the relay with a center off switch, and use it for 3 seconds just as I am ready to start the truck, it works great. The relay does click but am going to get new one just to see if the contacts are bad...using the switch, the truck starts right up with not missing a beat...go figure? Will update after I get new relay and install it, probably tommorrow.