A friend is stumped by a problem with his truck, so I thought I might get some insight here. I haven’t actually seen the truck, all that follows is from what he described, I’m just the messenger here.
The truck had been running fine on a used engine installed about six months ago. Then he ran it out of gas, it hasn’t run properly since. It cranks fine, but won’t start. He says it WILL start when spraying starter fluid into the throttle body, but only while the starting fluid is supplied. He also says he disconnected the fuel line somewhere near the engine, cranked the engine, and got good fuel supply (but no fuel pressure gauge reading). He’s done some logical things: new fuel pump, fuel filter, spark plugs and wires. No luck. Figuring that he’d sucked something ugly into the injectors, he decided to replace those with no change (yes, I cautioned him about throwing expensive parts at it with no clear reason). He reasons that he must be getting spark based on the engine running with starter fluid, and there must be fuel based on his test with the open fuel line, so he thinks it’s an electronic problem, presumably the signal to the injectors. This is out of my league…and my friend is a carpenter, not a mechanic. If he could get a scanner would this kind of problem register a code? Borrowing a scanner from parts stores is apparently not possible here in California…something to do with emissions testing, or so I’m told by Autozone, so the usual easy answer there doesn’t help in this case.
So, is there anything he can do without dragging it to a shop? He’s short on work (ie $$) but well supplied with free time, so more inclined to invest time instead of money…but he needs diagnostic help.
Did you figure anything out ? I have almost same exact problem:
1992 Oldsmobile Custom Cruiser 5.7 L V8
Was running fine till it stalled pulling into Dentists Office. Restarts had only very rough idle, giving gas killed it. After many tries, now won’t start at all, but cranks and idles for about 1 sec, especially with starting fluid, but dies as RPM goes up. Pressing gas peddle does NOT help-makes worse.
I have spark (judged by screwdriver in plugwire) and fuel (as judged by gas coming out of fuel filter when opened or cranking - but don’t know pressure). It was running fine before it stalled- no misses which is usually symptom of bum plugwires.
I replaced Idle Air Control (IAC) already, and inspected/cleaned Exhaust Gas Recirculation (EGR) valve (not dirty, depressing diaphragm pushes out air).
At this point I am thinking some kind of regulatory sensor that is shutting things down. I don’t know anything about these, but things I see in other posts or hear from people are Fuel Pressure Regulator (FPR- Don’t yet know if this car has one), Throttle Position Sensor (TPS - ditto), oxygen sensors, cam position sensors (guy at store said i didn’t have this - never backfired), or God help me, some computer control module. I do notice the “CHeck Engine Soon” light now, but didn’t see it before [What does this mean - “soon”, is something wrong or not?].
Alternatively, is there something stopping fuel between filter and engine (perhaps this FPR?
Please help if you can ! Dental patients are tired of looking at my butt.
@M80 - you probably don’t have the exact same problem. You’d be better off starting your own thread and description. Include all info about the state of maintenance.
@WesternRoadtripper - there’s no point in doing anything else until an actual fuel pressure gauge is put on it. Having fuel pump out tells you next to nothing. Your friend needs to get the fuel pressure specs and put a gauge on it. M80 could actually follow that same advice.
M80: You may have a similar electronic issue. I just don’t want to encourage my friend to throw parts at this problem without a diagnosis that points in that direction.
My friend is convinced the problem was caused by running it out of gas, and he now thinks it’s an electronic issue. Other than possibly killing the fuel pump, I don’t know what else could have been damaged directly by running out of fuel. Maybe this was a coincidence. I’d agree that some electronic control or sensor is probably at fault, but don’t know the first thing about diagnosing that. We’re not unwilling to DIY parts replacement in order to avoid the expense of towing to a shop and paying someone else to swap a sensor that we could change, but don’t know if it’s possible to be fairly sure what is at fault. Any suggestions on this would be sincerely appreciated. Thanks for advice!
Thank you Cigroller. I’ll see if we can borrow a fuel pressure gauge. Is there an online source for the proper fuel pressure specs, or would an auto parts store have that? If the pressure is too low, what could account for that, given the fuel pump and filter are both new?
Autozone’s free online repair info will probably give you the fuel pressure specs & test procedure.
As for the new pump - I don’t trust any part just b/c its new or rebuilt. Parts are commonly bad right off the shelf. I actually don’t expect the fuel pressure to be an issue. Its just that its a simple thing to check and needs to be eliminated as the problem before moving on & driving oneself crazy with other things.
As for the other things, I don’t know the injector set up on this engine - plenty of people here probably do & can say better than I if correct fuel pressure is verified.
You can buy a fuel pressure gauge for all of about $40. You might also find them among the loaner tools at an auto parts store.
Thanks again cigroller. Both options are easily available here for the fp gauge…I checked right after reading your first message. I may just buy one. We’ll start there and see what we find. FWIW: the pump is at least working as mentioned above, but I suppose it may not be producing the right pressure. I’ll post again when we have results. I am grateful for the advice.–Roadtripper.
Thanks for advice everyone. Westernroadtripper, have you checked your gas quality ? I went back today and replaced fuel filter, and retested fuel pump by pumping into bucket (before filter). I noticed a lot of water in gas, as well as some nasty yellow-brown-green color. I’d say about 5% of volume of gas pumped out by fuel pump must be water. I had just filled tank, of course. Irony is, this is the ONLY time I didn’t get the cheapest gas I could find. I must have a TON of water since I assume the fuel pump leaves a little space below for the nastiness. I dumped in 3 jars of isopropyl alcohol gas drier and tried to mix by jumping car around. Still won’t start. I think I need to drain the tank but, of course, GM in its wisdom neglected to put in a drain plug. I couldn’e get a siphon hose around fill tube neck angle and into tank, so i guess I need drop the full tank or else run the heck out of fuel pump to pump most our.
Does anyone know if I’ll need to replace anything like plugs or fuel injection parts after running a bunch of water through it ?
M80: As cigroller mentioned above, you should start a new thread so people can focus on your issue and respond to your findings. You won’t get responses here, though you might stay tuned to this thread in case there turns out to be some overlap. In your thread, start from the beginning and describe your situation fully. Good luck with it!–Roadtripper.
He might try this link and run a powered jumper wire to the fuel pump terminal (G) on the ALDL. This will at least verify if the pump is working correctly.
ok4450: thanks for the detail on jumping the pump terminal, and for the link. We do know that the new pump was working at some level. Before I got involved in this, my friend had opened the line somewhere near the fuel rail, probably not as safe as it should have been, and did get fuel supplied there. That of course is a crude measurement - we don’t know anything about the actual fuel pressure measurement. Cigroller’s advice was to get a fuel pressure gauge and post the readings, but I’ve not been able to connect with my friend today to pursue that, so we’re on hold, unfortunately.
So, IF a new fuel pump works, is it most likely putting out the proper pressure? Or could it be producing inadequate pressure? I presume it’s plausible that there’s a problem in the fuel line too restricting pressure, though he did replace the fuel filter. Would there be more than one fuel filter in the line? I gather from another recent post that injectors need a specific minimum pressure in order to operate, which makes sense. It may be a few days before we are able to investigate this further.
I had an '89 which is the closest I have owned to the OP year. It did not have a test port. It was a RPITA to adapt a gauge to it as the flared fuel line and nut connected directly to the TB. I actually fabricated an adapter using a short length of steel fuel line to the TB and some rubber fuel line w/hose clamps to splice in the gauge. Hopefully, by '93 they wised up and included a test port. I also had a heck of a time finding a TBI pressure range gauge at any auto parts store. All they carry now are the higher pressure gauges which were essentially useless at the lower readings for the TBI unit I had. I ended up getting a gauge from a friend who was in the gauge business and buying a brass T for it.
Thanks for the information Caddyman, TwinTurbo, and pete peters. Still waiting to hear from my friend so we can start investigating the fuel pressure. But your posts are useful and appreciated regardless. I still don’t know if the truck has the test port on the fuel rail, but I’ll keep the fuel filter fitting in mind. Thanks again.
If it’s TBI, while fuel pressure is important, for a non-start, you should be able to just look down the throat while cranking and see the injector spray pattern. If it’s doing anything other than dribbling and has a relatively decent cone shape, it should at least start. My older TBI had two filters; the standard in-line filter and a sintered filter at the TBI inlet. You unscrew the inlet nut and there is a sintered brass filter. Maybe your friend’s is the same and it’s plugged up? Check the spray pattern first…
@TwinTurbo
Thanks for this useful message, it’s exactly the kind of specific advice needed. I was thinking there might be one of those brass filters somewhere, but I’m not experienced on fuel systems so didn’t know where to look for it. But certainly that could explain why fuel may not be reaching the injectors even if the pump is working fine. Problem now is that my friend seems to have vanished, no call back now that I’ve got some information for him. I guess he’d rather have his truck collect dust instead of get fixed inexpensively. (But that’s an issue for another type of advice forum!). I appreciate your suggestions, thanks!
–Roadtripper
If the fuel pressure tests out ok, and it runs with starter fluid, and the fuel injectors have been replaced, it seems like it has to be some kind of electrical or sync problem.
You can’t start an engine if the valves are not synced properly to the crankshaft for example, no matter how good the spark and the fuel. A broken timing belt/chain would cause this problem. Sometimes these break – if they are already weak in the first place – when the engine sputters or backfires.
But the first thing is to confirm you have spark at the spark plug – which you must have or it wouldn’t start with the spray – and fuel being injected into the cylinders through the fuel injectors.
I finally caught up with my friend and his cantankerous Chevy truck. First of all, there’s no fuel rail and no test port for fuel pressure, just a fitting going into the back of what I guess is the throttle body - somewhat resembles a two barrel carburetor with what I guess would be called butterfly valves down inside. Two injectors point down into the barrels, two wires leading to each of the two injectors.
I now know two critical details I didn’t know previously. First, when he got it started with the starter fluid, it would continue to run as long as he kept the engine above 1500 RPM. It ran it for half an hour that way, smooth and steady, just like it should. But as soon as the engine was allowed to slow down, it would stop abruptly. . It seems to me that this probably points to something very specific…but I have no clue.
Also, pumping the gas pedal, or moving the end of the cable at the engine, did NOT create any spray from the injectors when the engine was not running but ignition ON.
Now here’s the unfortunate part. There was a little conflagration at one point when spraying the starter fluid (not me) which slightly melted the insulation on the wires leading to the injectors. Now the truck won’t start even with starter fluid, so I never saw the thing running. Capping it all is a dead battery.
The battery he can resolve. The wires are carefully positioned to not be touching and the insulation is compromised only slightly…no other visible damage.
So before the fire, is there something obvious to explain why it would run at 1500 RPM but not at idle? And then, what might the small fire have done to anything other than the wires considering that the damage to the insulation is slight…only little patches of copper are exposed, not the whole wire.
Here’s a photo - not sure if it will display larger than a thumbnail, but the file is larger. Couldn’t find instructions on uploading. Sorry it’s blurry but I think it at least shows the general configuration, with the wires that were affected by the small fire.