No-Start Nightmare!

[Zuiun]

Ok, I had thought all of my troubles were finally fixed, but I guess the Jimmy Gods have not yet finished toying with me.

Quick refresher~~

About a year ago, I started experiencing intermittent no-start problems with my Jimmy.

Here is how the problem presents: The truck will drive fine for a week, 2 weeks, maybe even a month or more. Turn the key and it fires right up -- no hesitation, no troubles and runs perfect.

Then, out of the blue, I'll have a hard start -- first turn of the key just cranks. If you open the door and listen, you can clearly hear that the fuel pump is NOT running (though you can hear the relays click). Generally, after a few tries, it will fire right up -- and will continue to fire up on subsequent starts.

A few days later, another hard start. Same as before. This time, though, it will likely happen more than once in a given day.

Maybe another day or two goes by, then again a series of hard starts.

Then it's daily. When it gets to this point, if the truck DOES start, it will generally stall within a minute or two of starting and then go through a no-start cycle.

Then the truck simply refuses to start at all -- maybe for 5 minutes, maybe for 5 days. Then, out of the blue, a turn of the key will produce a whine from the fuel pump and the truck will fire up.

I take it in to the mechanic, something is repaired (nearly everything in the fuel system has been replaced by this point) and the cycle will start over again -- the truck will operate perfectly for a few weeks, and then will rapidly go downhill with no-starts. Often, simply the act of towing it to the mechanic is enough to "fix" it for its next cycle, with or without any repair -- indicating that all of the repairs I've done so far have not touched the problem.

Therein lies the frustration -- if it was ALWAYS intermittent, I (and the mechanics) would have a better shot of figuring it out. But what the hell would be causing it to fail in cycles like that? It just doesn't make any sense!

It doesn't seem to make any difference whatsoever what the outside temperature/air pressure is. Driving conditions are always the same -- I take it to work and run errands. I buy my gas consistently from the same few places (and have another vehicle that runs fine without fuel problems).

I know you guys have tried to help out in the past, but I need some real "out of the box" ideas here -- none of the ideas previously presented on this forum have worked (though all have been tried -- do a search for topics from "Zuiun") and the problem has stumped my local mechanic and the mechanics at a GM dealership.

I can't drive this vehical -- because I never know if I'm going to be stranded. And I can't sell it, because I have no idea if it's going to ever start for the dealership.

Any thoughts???

Thanks in advance!

-- Robert

[blazes9395]

o.k, this is how I would go through this one. First, I would connect a simple small 12 volt test light from the pump connection at the tank and run it to the dashboard area - keep the light on the dashboard, so it can easily be seen when driving. Note this can be done with a scanner, but I assume you don't have a scanner, so this light method will do the trick. Drive the truck and note the light when drivng starting etc, keep an eye on it. If the light flickers, does not come on, or goes off and goes on, its not the pump, something with wiring - electircal. If it does not go off and is solid when the key is in the run position all the time, your problem lies on the fuel pump side, or its related components. I think you mention that all the wirng has been replaced? Exactly what has been replaced? Wiring from the relay to the pump?, wiring from the PCM to the relay or both? Have you or your mechanic ever tried just running the pump through the test port for the pump and making sure it works as it is required? Is this pump a GM pump or aftermarket pump. This sounds like a bad pump to me...could be wrong. Have you ever tried tapping the pump or tank, when it did'nt work. This sometimes gets the pump going if it is the pump.

[Zuiun]

Do address your questions first, I'll see if I can recall all that has been replaced (I don't have the paperwork in front of me):

-- Fuel pump (x3)
-- Sending unit
-- Relays
-- Wiring (pump to relays)
-- Fuel filter
-- CPI injector
-- Ignition switch and coil
-- Battery

The problem was first diagnosed as a fuel pump, so that was the first repair. When that didn't solve it, the new pump was warranteed out with a new one. That still didn't solve it. A third was tried (somewhere in the midst of the other repairs). I don't recall which pump is the most recent -- aftermarket or GM (both have been tried).

During one of its longer dead times, I did hook a test light to the wiring plug back near the pump and I am getting power back there with every turn of the key. I'll look into your suggestion about hooking a light up to test the signal while driving.

The suggestion to "thump" the pump and the tank has been tried -- no difference.

The thing that is most frustrating is how cyclical the problem is -- it will work perfectly for awhile, then gradually start to fail. Once it fails, it will usually stay dead for a couple of days, then decide to start running again -- and then it's perfect for another couple of weeks.

When this problem first presented, my mechanic thought I was insane, because generally it was running fine again by the time it was towed in (lending credibility to the suggestion of tapping the fuel tank). But since then, there have been instances where it hasn't run after being towed -- and there have been instances where it has fired right up after having just sat dead in the driveway for a day or two (not bumped or moved it at all).

The thing that gets me -- and the mechanics -- is that it isn't consistently intermittent. It just doesn't make any sense whatsoever for it to run perfectly for weeks, then gradually start to fail -- then start running fine again. Does anyone have any other ideas about what might be causing this kind of problem? I mean, to this point, every effort has been focused on the ignition and fuel systems -- what else might cause this sort of cyclical behavior? Computer? Alternator? Ghosts?

-- Robert

[rlith]

Have you checked the ignition switch? Your symptoms sound similar.

[Zuiun]

Originally Posted by rlith

Have you checked the ignition switch? Your symptoms sound similar.

Yep, that's on the list of repairs that have been tried - as well as the ignition coil.

I'm tellin' ya -- this is the most frustrating thing. I have two separate GM certified mechanics who are at a loss, which is why I've been posting to forums, hoping that someone out there might have had a similar problem and can clue me in (everything major has been replaced, so it's got to be some stupid, simple little thing!).

I don't know what else to try, short of getting a priest to perform an exorcism!

-- Robert

[rstyrlz]

I went through a similiar problem with my 91 2.5L tbi S10 My problem was a bad fuel pump and after the new one was installed it would fail every now and then. check all your ground wires. even under the hood .

[storme]

Have you received any new information? I have a similar problem, but the cycle of no-start is usuallly preceded by the "security" light coming on. Then, it will turn over, but not start. After about 30 minutes, when I hold the gas pedal to the floor and crank it, it fires up. But, just as in your case, the security light does not always precede it, nor does flooring it always work, and there seems to be no other consistent indicator of trouble.

Cath

[BlazerLT]

Have you checked fuel pressure when these problems start?

This could also be from a faulty alternator not charging up the battery and the battery doesn't have enough juice to prime the pump properly.

Also smell your oil dipstick for gas.

[jsgold]

If you can rule out pressure and CPI unit might try the ignition module itself. i don't see it on your repair list. Mine went out some time back, random starts, thought is was a fuel problem. Nope. It sits in your distributor. Just a thought...

[DzdnCnfsd81]

I had a problem very similar to yours with my jimmy, and after contemplating an expensive fuel pump replacement (because my fuel pump wasn't engaging), i changed my relay switch. the switch was 10-12 bucks and i have had no problems since.

[recncru1]

i didn't see oil pressure switch.I did see sending unit though......did you mean oil pressure switch? The oil pressure switchcan shut the engine down if it thinks there is no oil pressure.It does so by turning the fuel pump off.

[1993 Jimmy]

This might sound crazy but my 93 Jimmy has a problem that is kinda the same, when mine does not start I pull the coil wire and either swap ends or just put it back on. After that it will start fine for a few days, weeks, or even months. I have not had the money to start changing parts yet, but it is something to check into. What kind of spark plug wires are you running on yours? Some people have said that it makes a diffrence.

[psjermey]

I have a '93 Astro that had a problem something like yours except when it DID decide to start, it flooded like crazy. Flooded to the point that it one time loaded the exhaust will fuel and when it did fire, well, the neighbours heard the muffler explode 1/2 mile away.

Anyway, it was a fuel injector spraying straight down instead of in a circular pattern. Replaced it and it's worked fine ever since.

[cbrewer]

I have this problem also. I took it to Auto zone they checked it and he said it was crosion on the terminals my husband put some grease on them didn't clean them like the guy at AZ said. He said to let them soak in baking soda and water? Hav'nt tried that yet. We do have a new battery and still does the same thing.

Originally Posted by storme

Have you received any new information? I have a similar problem, but the cycle of no-start is usuallly preceded by the "security" light coming on. Then, it will turn over, but not start. After about 30 minutes, when I hold the gas pedal to the floor and crank it, it fires up. But, just as in your case, the security light does not always precede it, nor does flooring it always work, and there seems to be no other consistent indicator of trouble.

Cath

[darkarlaw]

Originally Posted by Zuiun

Ok, I had thought all of my troubles were finally fixed, but I guess the Jimmy Gods have not yet finished toying with me.

-- Robert

Check thread below: "97 no start no crank": intermittant. gradually got worse, new alt, new ign wiring, new starter, new batt and cables, cleaned ground conn on motor, turn key nothing but heard relay pic in glove box, did not hear pump come on or run.... I kept reading back to page 52 or so and found a guy with much the same, 4 mechs found nothing until one unhooked all the control module(computer) wiring harness plugs and rehooked them, like majic it started and works now. It worked on my '97 too. Sounds like a pump, press, or relay,filter, loose elec conn, or ground problem. Try this, it's quick and easy. Good luck..