Hi all, after reading several threads and searching over the forum posts for quite some time, I've decided to make my own post in hopes that someone might have an idea what is going on with my truck. Please let me know if there's an identical thread and I'll delete this post but I could not find one.

Issue: While warming up the truck after replacing the rad to burp the coolant, the truck stalled out after getting warm and and has refused to run since.

Where I'm at currently: I think I've managed to isolate the issue to something in the electrical system with regards to the fueling. The fuel pump does NOT run while the engine is cranking and FP is jumped to B+ in the diagnostics port.

Diagnostics I've done so far:
•Truck ran when carb cleaner sprayed in the throttle body
•Sparks on the plugs when pulled and tested. They were bone dry as if no fuel reached them.
•checked the Circuit Opening Relay, jumped the battery to power terminal on the body harness with no luck. The relay clicks as it should when cranking.
•checked all the fuses in the engine bay
•checked the EFI relay
•checked the fuses in the kick panel
•fuel pump itself is new (3 months or so old), tank is new, sending unit is new, fuel filter is new
•fuel pump runs when given 12v from a battery
•when using a multimeter on the body-side harness of the fuel pump at the fuel pump itself, 12V is present between power and ground on the terminal
•checked the B+ in the diagnostics port for power and it had 12v
•the tank is just about full with new fuel
•tested resistances as per the FSM for the AFM and they checked out
•new coolant temperature sensor

Running out of ideas as to what it could be, any help would be appreciated. I am at the point where I have no idea what else it could be.

 

You need to jump Fp and B+, AND turn the key to on to get the fuel pump to run.
You can also hear the fuel pump run, if everything is working right, by turning the key to STArt, but not pushing in the clutch pedal or the Clutch Cancel Switch. It's a quick check of the fuel pump, and the STArt half of the COR. Jumping the Fp to B+ and turning the key ON checks the "run" half of the COR, and the fuel pump and the electrical system.

IF the fuel pump runs when it should, but the plugs are dry, it sounds like the injectors aren't getting their +12 or ground. Often the resistor pack that feeds the ground from the ECU to the injectors when they're triggered can go bad. Or the wiring from the ECU to the injectors. Check the FSM for how to ohm this circuit out.
You can see if the fuel pump is pressurizing the system by pulling the return line off the Fuel Pressure Regulator, at the rear end of the fuel rail. Put a clear piece of tubing on in place of the return line, and put it into a container to catch the fuel that will, hopefully, come out. If no fuel, but the fuel pump runs, trace it back.
Do you have fuel at the Damper at the front of the fuel rail? Do you have fuel at the output of the fuel filter? Etc.
Did you put the fuel filter in the right way when you changed it? It SEEMS like it goes in backwards, IE the arrow indicates the flow indicates that the fuel is going to the rear of the truck. It's not. It's just the way they designed the lines to/from the filter.

Make sure the fuel tank is well grounded to the chassis/body. The fuel pump receives it's ground right there at the circular plate it's mounted to. Make sure the tank's ground, and the circular mount's ground, to the chassis/body is good.

Hope something in all my babbling is of some small help...
Pat☺

 

Hi Pat, thanks so much for the suggestions!

I should have specified that with the jumper in, I did indeed have the ignition set to ON and even tried starting the truck to no avail.
(I definitely could have messed something up so I'll retry tomorrow when this darn rain goes away)

I'll check over the the resistor pack, injector wiring, tank grounds, and fuel pressure along the way as well.

With regards to the fuel filter, I had it installed by a shop over a month ago... I would suspect that might be a more immediately noticeable problem but I'll double check that too.

Will report back soon with the results for each.

 

You've covered most of the usual suspects. You should be able to hear the fuel pump running with the jumper and key-on. You've confirmed 12v to the FP connector, now just confirm that the FP connector goes somewhere. With key-off, measure the resistance to ground at the FP terminal. I get about 3.4 ohms https://www.yotatech.com/forums/f116...-quits-312747/ . If you get "high" resistance, then a wire is broken between FP and the pump (by providing 12v to the pump, you've (more or less) confirmed that you don't have an open winding in the pump). If you get very low resistance, well, that would have blown the EFI fuse. (And accurately measuring resistance less than 3 ohms requires more than a mere multimeter.)

If you can hear the fuel pump, running a substitute fuel return line to a container as 2ToyGuy suggested will confirm fuel is flowing (I get about 1/2 liter/minute; if you get substantially less I'd worry about a blockage.)

 

Thanks for your help Pat and Scope!

I'm glad I tried the easiest thing first (unplugging and testing voltage all along the way.

I'm not sure what I fixed, but when I plugged it all back together, the fuel pump started right up as I had the jumper in. Took it out, started the truck as per usual and voila, it worked.

I guess the lesson I learned is that truck wiring diagnostics is somewhat like tech support, always try unplugging it and plugging it back in.

 

curious if the CEL was on when it didn’t start and the pump wasn’t working. with my ‘87 22re, if the CEL doesn’t light when the key is turned to start, the pump will not run as it is supposed to.

 

Glad it's working again! That's the whole point in any event

Quite often, these older trucks develop corrosion on the contacts in the connectors. The environment in there is harsh. When you pulled whichever plug fixed it, and plugged it back together, you "wiped" the contacts. Bingo! Trouble solved.
The contacts can also work their way loose in the plug. It might be you had a contact pushed in a plug, not making good contact. When you plugged everything back together, you pushed the contacts back down into the plug. I have that problem with the 4WD switch wire coming out of the transfer case, in my 87 4Runner. I'll have to replace the plug and contacts eventually. It insists on pulling out of the plug, and just not making connection.

A bit of advice, if I may. Whenever *I* unplug a plug in my trucks, I put a small dab of the famous silicone dielectric grease into the female side before I plug them back together. It will keep the contacts from developing corrosion for a much longer period, as well as making pulling it apart the next time a lot easier. That includes the plug wires at both ends. ANY electrical connector. So far, *knock wood* no corrosion troubles in any plug. I think by now I've probably unplugged just about every plug in both my 87's.
It also helps preserve rubber bits and pieces. The o-ring on the idle adjust screw, the small water hoses under the throttle body, and so forth.

Anywho, I'm glad it's going again as it should. Now go out and enjoy it! These trucks just don't like to sit in a garage. They WANT to get out and boonie-bounce
Pat☺

 

Hi Wally, the CEL was not on if I recall correctly.

 

Hi Pat, thanks for that suggestion! I'm gonna run out and do that, the climate here in Nova Scotia is very humid and salty so anything that can corrode, will corrode.
Got the truck out in the woods the next day and it worked like a charm!