When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I'm working on a friends 93 F150, 5.8 & e40d transmission. I've corrected a few simple problems: alternator, battery, key cylinder and ignition switch.
The truck would start & run about one in five tries but eventually would only crank but not run. The fuel pump was running continuously with the key in the run position. All my research here led me to the ECM.
I pulled the ECM & found all three capacitors leaking, one had a burned off leg & had burned a trace below it. I replaced the capacitors with the same values & tried to bridge the trace. The truck ran but quickly showed the same behavior - fuel pump running continuously & no start.
I sent the ECM out for repair and received it back quickly. I installed it and again the fuel pump runs constantly & truck won't start.
I emailed the company who worked on the ECM, telling them of the same problem. Their response was that "it has to be something external" and that he tested the fuel pump function & it was working as it should. He acknowledged that he got my note about the pump running & no start condition.
Here I am, looking for something "external" as in wiring or a stuck relay. I've swapped the relay 4 times with the same result. Two pins on the relay socket are constantly hot with the key in the run position.
I've reached out to my Ford friends to borrow an ECM for testing but haven't found a match. Nothing in the local wrecking yard either.
From the knowledge I've gotten about this issue it still points to the ECM. I would love to be wrong and find the issue in the wiring but I still think it's in the ECM, possibly the fuel pump transistor. I can't identify that transistor though & wouldn't know how to test it if I did. Any help moving forward would be greatly appreciated. Mike
When the PCM has an internal fault that causes the pump to run constantly it is because the processor never finishes the engine startup routine, somtimes when caps fail they do other damage that can't be repaired... If the PCM is healthy the engine should run on starter fluid. A stuck relay or wiring short can also make the pump run constantly but just because it is running doesn't mean it is pumping fuel, have you tested fuel pressure at the rail? If the pump was changed but miswired it would push fuel back into the tank, and of course an empty tank is another possibility.
When the PCM has an internal fault that causes the pump to run constantly it is because the processor never finishes the engine startup routine, somtimes when caps fail they do other damage that can't be repaired... If the PCM is healthy the engine should run on starter fluid. A stuck relay or wiring short can also make the pump run constantly but just because it is running doesn't mean it is pumping fuel, have you tested fuel pressure at the rail? If the pump was changed but miswired it would push fuel back into the tank, and of course an empty tank is another possibility.
The pump hasn't been changed. This truck is unmolested, no crazy splices or wire nuts anywhere.
I'll check pressure at the rail. I think the pump should prime for two seconds wether there's fuel in the tank or not, IE: it's not pressure that shuts it off in the initial start but a timer on the board.
When the pump shuts off as intended the truck starts & runs fine. It shifts fine as well & overdrive can be turned off & in by the button on the shift stalk.
This truck was starting & running but slowly became worse.
I'll check pressure at the rail. I think the pump should prime for two seconds wether there's fuel in the tank or not, IE: it's not pressure that shuts it off in the initial start but a timer on the board.
Correct.
Originally Posted by ~X~
When the pump shuts off as intended the truck starts & runs fine. It shifts fine as well & overdrive can be turned off & in by the button on the shift stalk.
I recently repaired, and eventually replaced an EEC-IV in a truck with exact same issues.
Randomly would not start with continuous fuel pump running.
Then would start and be fine.
The repaired EEC was faulty, replaced with another known good one.
My ECU threw false lean codes and had intermittent misfires when the caps started going out. Then before it’s end it started running the fuel pump constantly. You need to get the pinout for your ECU and check all the grounds to it if you haven’t already. Check the wires going in for shorts. It’s very possible the ecu they sent you wasn’t right because that’s pretty common but it’s also possible an issue with your truck overheated the new one. Especially if it worked fine at first IMO.
My ECU threw false lean codes and had intermittent misfires when the caps started going out. Then before it’s end it started running the fuel pump constantly. You need to get the pinout for your ECU and check all the grounds to it if you haven’t already. Check the wires going in for shorts. It’s very possible the ecu they sent you wasn’t right because that’s pretty common but it’s also possible an issue with your truck overheated the new one. Especially if it worked fine at first IMO.
This is the original ECU that was sent in for repairs, all original numbers and has not been swapped. As it is now I can't get codes using an Innova 3145. It works works on my Explorer, the repaired ECU refused to scan.
This is the original ECU that was sent in for repairs. As it is now I can't get codes using an Innova 3145. It works works on my Explorer, the repaired ECU refused to scan.
Thank you for the responses, all of them .
my money is on they didn’t repair it correctly. Or the board was too damaged to be repaired properly. No connection is a sign of ECU failure. When you turn your key to the on position the check engine light should illuminate. Then while cranking the engine the check engine light should go out if you didn’t already know that.
The PCM was sent in & repaired. I think he missed something during testing.
These guys can't fix hardware faults with these PCMs outside of generic things like blown capacitors, the core computer parts.. besides being purpose built for Ford(not generic) have been out of production for several decades and simply don't exist anymore. I also seriously doubt they test all PCM functions, in fact I'd be surprised if they test much of anything. You have to realize a test fixture for something like this is a very specific piece of equipment and would be very complicated, there are hundreds of different calibrations for these Ford EEC4 PCMs alone and each one of those would require different test software to fully analyze. I worked in high tech manufacturing for many years on the engineering side, we had test fixtures like this for all the equipment being manufactured that I used, debuged, and repaired on a daily basis. So you might say that I'm more than a little familiar with this type of thing.
Even if that company has something like this your PCM has an intermittent fault... the worst kind of problem to find. It may have passed the bench test.
This is the original ECU that was sent in for repairs, all original numbers and has not been swapped. As it is now I can't get codes using an Innova 3145. It works works on my Explorer, the repaired ECU refused to scan.
Thank you for the responses, all of them .
I got tread tired of spending time and skint knuckles,, so started spending a little $$. I found a match on ebay. It worked a week or 2 then had an issue. Pulled it,, opened it and 1 cap was bad. Replaced all 3 just to sure and It's been running well for close to a year now. Before the cap replacement while waiting for caps, delivery, I started looking at another small issue. 3rd brake light was out. I traced the wire from under the hood back. Found it severed as I had just ran it on the outside of the loom that covers all the wires headed back. While fixing that wire I found the loom had a quarter size chunk busted out and 2 wires from inside the loom were not broke,, but skint. This damage was in the frame but as I looked I found the top bracket for the rear shock had come down and whacked the loom,, likely I shouldn't haul that much wood at 1 time. Cleared all that mess up and now have a functional PCM with no intremittent hic-ups. There is one of our brothers on here that has had good luck with SIA Electronics. https://siaelec.com/get-a-quote/ Let us know how goes it with you repair
OOh,, one more thing. After dealing with the wiring issue I found 2psi at the rail. My guess the skint wires had also likely shorted/damaged the fuel pump. While preping for that replacement I also found when removing the one tank I have/rear it started weeping gas under each strap. So seems that hauling too much wood cost me PCM,,repairs, wiring repairs,, new fuel pump and tank.Wheeeew.
Just replace the gas tanks
They always did rust under the straps
I don't think hauling wood was the problem
When the processor craps out and the pumps run constantly, it does "this" to the internal hose on the fuel pump sometimes
Rezvani's Latest Post-Apocalytic Monster Is a Ford F-150 Raptor Underneath
Slideshow: Called the Fortress, the 850-horsepower pickup combines Raptor underpinnings with military-inspired features, survival equipment, and a starting price of $285,000.
