HELP!!! My truck hasn’t run for over a year and no one seems to be able to tell me why. The fuel pump supposedly has 10 lbs of pressure, it has new fuel pump relay, new throttle body, and probably more new things (can’t remember exactly). It will start up normally and then it will act like it’s not getting fuel and within seconds die. If I keep my foot on the gas and kind of pump it (I know it’s EFI) it will try to keep running, but will die, and it really gets rough toward the end like the whole engine’s going to fall out. The truck has 300K+ on it but the engine was replaced about 10,000 miles ago. It still has a lot of original equipment. Should I just let it die a natural death? I love my truck.
It may be a faulty oil pressure sender
The fuel pump run circuit is controlled by that switch.
Have you changed the fuel filter? I would check that first.
fuel filter was one of the first things changed, oil pressure sender? Will that keep it from running? Just so I understand, how does that affect fuel?
It’s sitting at the local “mechanics” now and they don’t seem to know what to do with it. They wanted to take off the valve gaskets and check there, but it just seems to me to be either an electrical or fuel mixture problem, but I’m not a mechanic.
An above average mechanic should be able to quickly look at the wiring diagram of the fuel pump and probe a few connections under the hood to diagnose the cause for the fuel pump failing to function correctly. If the local “mechanics” have not tested and verified fuel pressure they should leave the valve gaskets (cover) alone.
The fuel pressure should be considerably more than 10 lbs. if the engine has fuel injection. To see if this is a fuel problem (and it sounds like it is) you should be able to keep the engine running by spraying short bursts of starter fluid into the intake. If that keeps it going you have proved there is fuel delivery problem. Perhaps the regulator has a problem.
There are a number of EFI incarnations, this one is likely to be TBI. The pressure is on the low end s/b more like 14 lbs IIRC. That is probably not why it won’t stay running if it holds that pressure constantly.
I’ve seen this a few times on the 350 tbi motors- there are two temperature senders one for the gauge one for the ECM (computer). When the computer one fails, it dumps lots of fuel and will barely idle. It’s a cheap part and not hard to replace. If i was going to throw a part at it, that’s what I’d do.
Will have them try the starter fluid idea. From what I’ve read the pressure should be between 9 and 14, but then I’m not sure that 9 lbs if a constant pressure or not since I wasn’t there when they tested it. As far as the temp sender, I will have them check those for sure. One is located on the driver side cylinder head? Where’s the other? Someone did mention the wire could be broken. The truck IS 23+ years old. Will let you all know when I find out something. REALLY appreciate the suggestions!!
Re pressure, if it drops below 10 the truck would probably lurch badly but idle normally.At this point it seems there is a good possibility there is virtually no pressure within a few seconds after it starts. The pressure needs to be monitored when the engine stalls. But it is so very easy to jumper the fuel pump and give it a try. If it runs normally the problem is in the ‘fuel pump run’ circuit.
Well, I decided to go get my truck today. They got it “running” but just barely. They replaced the: rotor, distributor cap, spark plugs, wires,pick up coil, ign control module and threw some seafoam in it. It doesn’t die like it did, but it is missing and definitely not running on all cylinders. I made it up to 45 mph on the way home (downhill) but it had a bad time going uphill and couldn’t get it over 30mph going uphill. backfires a lot when you let up on gas and wants to die when you slow down for turns. Checked the wires and they seem to be right. "mechanic " still thinks it’s valve problem or something, but it just doesn’t seem logical to me.
the oil pressure sending unit is also a fail safe if the engaine stalls out it shuts off the power to the fuel pump relay, i would start with all the simple stuff like a vacuem leak
Hmmm well, got under the hood to do some checking and seems that no one bothered to tighten the dist. cap down, thinking maybe that could cause some misfire problems. Haven’t messed with it yet, but hopefully that will at least help with the problem!
Tightening the disty cap should help a lot. If you still have the problem I suggest you look for a fuel problem. If the oil pressure switch is causing the trouble you can try bypassing it with a jumper to see if that helps. It would sure be a very good suspect in my book. The fuel pump is another possibility. The pressure should be checked out, as was already suggested.
Inside the fuel tank, the fuel pump is connected to the hard exit pipe by a length of silicone fuel line. I have seen this line split and leak, causing a big drop in fuel pressure, starving the engine of fuel…There is enough pressure to start and idle, but when you ask for more power, fuel pressure drops even more and the engine stalls out…Check fuel pressure under load and compare it to the specs for your engine…
So, I have a 95 Chevy C1500 Silverado xcab with the 5.7 EFI. I had to change out the whole distributor to get mine from doing what yours is doing. Hope that helps.
Tommy , your info might help someone but this is an 8 year old thread . You can see the dates of replies on the right side of the screen.