At a loss - 88 Ranger Cranks with Spark but No Fuel

[kuso]

I recently picked up an 88 ranger 2.9 4x4 5spd with a total spaghetti mess of a wiring harness (both inside and out.) It's a nightmare. I do not think the ECM is getting any power as the engine light does not turn on, the only light on the dash is the battery light. I have tried both harnesses that came with the truck and neither seem to fix the issue although it will run with gas in the intake. The fuel pump does not prime but I know it runs because I ran wires directly from the battery to the HPFP. Even with the fuel pump running 24/7 it still did not fire off. The injectors have 12v on both pins, I have tried the following; jumping the pins at the eec relay(the fuse links are good), new relays, inertia switch bypassed, two different eec's installed, and still nothing.

 

[Brain75]

I believe even on 1st gens the the injectors are continuously powered and the ground is interrupted on / off for the spray pulses... you said you are getting power on both pins - that isn't right... if you can figure out why the ground pin is getting power, then check resistance to ground on the ground pin of each injector - work on it till you are getting power and ground on each injector.
Easiest is a noid light once you think you got it straight.

Do you hear the injectors clicking while trying to start it?
If the throttle cable is not stretched out so much as to prevent WOT, then going WOT during crank will turn off the injectors (clear flood mode) - so you can usually tell by ear by trying a normal crank and a WOT crank... no differences mean no injectors firing or you aren't achieving WOT.

 

[SenorNoob]

Depending on how you check it, You could have power on both sides of the injectors if the PCM isn't grounding them. There would be 12v thru the injectors all the way to the PCM.

 

[kuso]

I do not have a set of noid lights to check but I'm fairly certain the eec isn't grounding them because its not turning on at all, or at least there is not an indication of it being on. I just replaced the ignition switch and still am not getting an engine light when keyed to the run position or any fuel pump.

 

[Brain75]

2 things come to mind... check the ground of the pcm for corrosion itself (the outer case and like pin 1 or 60 - one of the ends) go to a ground on chassis or crack open the case of the pcm and see if the capacitors have given up the ghost after 30+ years.

 

[SenorNoob]

Yeah, gonna have to check all the power and ground lines to the PCM.

Pins 20, 40, and 60 are all grounds. Technically 20 is a case ground, 40 and 60 both go straight to the battery.

1 should be power directly from battery for memory. 37 and 57 both come from the same pin on the EEC relay that powers the injectors.

 

[Terrys87]

Radio shack went out of business but if you can find a similar LED, this works great for a noid light. You have to pay attention to polarity. I paid a whole $3 for the led. https://www.yotatech.com/forums/f116/3-noid-light-22re-270857/ I fought an injector issue and it was corrosion in the harness. Resistanc checks passed. A 50 strand wire with 49 broken wires will still pass resistance checks.

I have not done it on a Ford injector, but I have used a syringe, a tube that fits over the syringe and the injector and the little square 9volt battery. With pressure on the syring and a wire to each connector to the injector, it would open the injector and spray. https://www.yotatech.com/forums/f116/fuel-system-cleaning-287490/

There is a ground wire coming off of the ecu. I find it a good idea to go thru with a wire brush and scrub all ground connectors and to the body or frame. There are actually quite a few grounds on these trucks.

 

[kuso]

Thanks for the insights guys. I pulled the harness and did a full continuity check of the engine and cab harnesses and reestablished the grounds. While I was on the cab harness I noticed that the 10 pin connector that comes out of the cab to join with a chassis harness had some wires and pins missing and one of those was the black and pink fuel pump wire. Someone had joined in the pink black fuel pump wire into the orange wire that I assume runs the lift pump which was severed. I used a spare harness to rewire and repin it to the connector in the proper place. Still have no clue what the other wires are for but sure enough it primed for two seconds then fired right up.

Interestingly, I still did not get an engine light in the run position, nor do I have a tach. It is worth noting that it fires right up but the truck runs pretty rough, seems as if its misfiring or down a cylinder and does not want to idle or rev readily. Could be old gas but any insights would be appreciated.