92 GMC C1500 V6
No fuel to injectors, I have replaced pump, strainer and filters. Changed the filter first and ran fine with a few misses (likely no fuel?) then just got the new pump and strainer on today. Again drove fine with a few misses. Got down to the river to fish and went to leave and once again no fuel to injectors, sniffed the vacuum hose and it had no gas smell.
Suggestions? Feels bad to have to have my truck toed again lol.
This could be caused by any one of a number of things, but a wild stab at it might be an iffy crank position sensor.
There should be a fuel pump test pin in the ALDL connector where codes are pulled. A jumper wire from a power source to that pin should cause the pump to run. This is ONLY a test so do not leave any jumper in place.
If the pump runs and the engine starts then the problem is likely in the fuel pump control circuit which is also affected by the crank sensor.
You can do a net search for info on the connector and which pins do what. That would be easier than laying it all out here.
@ok4450 I’ll check it out later today, is there a basic way to tell by OHMs? I’m also going to do impedance test on injectors.
Is your fuel pump getting power?
Like the others have already mentioned I would suspect power to the fuel pump is being interupted somehow. It could be as simple as a faulty fuel pump relay causing the trouble. Bad relay contacts can cause that kind of issue. Another possibility is a bad power connection in the wiring to the pump. Problems like this are usually fairly simple things to fix but easily get overlooked.
Power to the injectors could be the problem if the pump circuit is okay. You shouldn’t have to check the injector coils. It would be the power for the injector circuits that would need to be checked.
I can hear the pump when the key is turned and when trying to start the truck. When I replaced the pump I cut an access panel on the bed so I have straight access to it.
I’ll check my book for the fuel injection circuit.
An update on this, after putting gas onto injectors she started up (a little rough at first, one miss). Not gonna trust it much until I know for sure.
I suggest you try swapping the fuel pump relay. That may just clear the problem up. If there are others like it you could even try swapping them.
I think we’ve been here before on this truck but just for a refresher, the oil pressure sensor has a fuel pump by-pass switch so that when there is oil pressure, current flows to the pump regardless of the relay. So even if the relay was bad, the pump would still work if there was oil pressure while running or after extended cranking. So is it that there is no fuel to the fuel rail even though the pump runs? Fuel pressure regulator? Or is there fuel in the rail but the injectors are not being told to open by the computer?
(I’d better stay out of this come to think of it. Does it even have the fuel rail set up?)
@Bing its the throttlebody type (if that name is correct). Pretty much two injectors with two on each one.
I do recall that posting you mention @Bing and remember the oil pressure switch that bypassed the fuel pump relay.
Not gonna lie I’m a little lost now.
First thing to verify is that the SECURITY lamp on your dashboard is not illuminated when the problem occurs.
Second test would be to see if fuel pump has power. Jumping the ALDL pin as OK4450 suggested is the easiest way although you mentioned hearing the pump run, it could be interrupted after initial cranking due to several reasons.
Next I would check fuel pressure although it’s a pain on these TBI units. Quick and dirty test, disconnect fuel line and run into container, then try cranking…
I’m not going to lie either. I know nothing about TBI and not sure I’ve even seen one, so disregard anything I’ve said.
A look at the schematic does show an oil pressure sensor involved in the fuel pressure circuit. The schematic is fairly complicated and it would be nightmarish to sort it out on the internet. There are a number of fuses involved in the operation of the oil pressure sensor, ECM, fuel pump, etc so it might not be a bad idea to check all of the fuses (every single one) and verify beyond all doubt that a lowly fuse is not the cause of this problem.
A long overdue update on this (gotta love pulling 12 college credits and working). Did a noid light test, tested OK (pulsing light). Plugged the injectors back in and she started right up. Not for sure if this means bad connection on top or what. Drove around the block and did not get a single misfire.
Fingers crossed and keep a cell phone with you for a while.
Indeed even got roadside after 2nd tow home hahas. Gonna go ahead and do fuel pressure test with my Dad tomorrow, might possibly pull off injectors and check for buildup.
If the engine is running and then dies on you then the trouble is very well could be with the oil pressure switch that supplies power to the fuel pump after the engine gets running. You could bypass the switch contacts to see if that stops the problem. Pulling the injectors isn’t going to do anything except cost you needless time. You would be wise to invest in service manual to help you with this trouble. Ebay is a good place to find them at reasonable prices.