99 f350 no start, no wts or cel. pls help

[jsbelectro]

*guys, new here posting, but have got a lot of help from these sites working on my truck.... so my problem started with my truck dying on me in the morning, started it back up and it ran for 5 min until it died again. after that the relay behind the radio quit clicking which is the*fuel*pump*relay. so I have no power to the fuel pump. since then I have been doing test after test. I have checked all fuses under the hood and in the cab. all are good. swapped relays around, tested the computer plug for all grounds and positives and all passed. I have done basically every test I can think of. so I purchased a new*pcm, installed it with batteries disconnected of course. and nothing. very upset and almost want to take it to the dealer, but I cant. I'm a long time mechanic and this is just really getting to me.*fuel*bowl*heater*and fuse is fine by the way. please help....

 

[TyCorr]

If you put a known good relay in there and it didnt fix it you should have started checking elsewhere. Did youbtest the fuel pump and make sure its not dead?

 

[jsbelectro]

Yea, I hot wired it at the fp relay and it worked, I also manually grounded the computer controlled ground, and the circuit worked fine. Relay clicked and pump came on, but still no start. I even manually grounded the computer controlled IDM ground and still no start

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[jsbelectro]

I have downloaded all the wire schematics for the pcm connector, the 42 pin connector, obd connector etc. I have tested all the grounds, the one constant 12+ and the 3 grounds. All tested good. I am kinda stumped though on a couple things. With the key off when I go to check some of the computer controlled ground circuits at the pcm plug like glow plug, fuel pump relay, and wait to start light, I get about 11volts+. But when I manually ground those circuits, they will work as they should. Is it because when I'm using my dvom on a grounding circuit, is it completing a ground or completing a circuit, or am I reading some residual back voltage from the coils in the relay associated with that ground. The second stumper is when I manually ground one of the ground control circuits is that there is no arcing or sparking indicating a ground line has a short to +. I have taken the under the hood fuse/relay box out and inspected it, and it seems good. That is without completely tearing it apart.

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[TyCorr]

Is the fuse block any good?

The factory fuse blocks get corrosion in them and it causes dome crazy things to happen.

 

[PsdPullerJr]

I had a fuse crack on me one time, no wts light, no fuel pump, no start. Fuse looked perfectly fine. It's out under the hood but unless you physically checked the fuses, swap the PCM fuse with the radio fuse. I think they are both 30 amp, I can't remember for sure now without looking, but that fixed my problem. Fuse wasn't burnt at all, just had a hairline crack i had to put under a microscope to see.

 

[jsbelectro]

Makes me wonder....I did take the fuse box out to check the wires goin indide, but didn't take it apart. I will do that today. As for all the fuses, I used a test light and a dvom and they all tested ok. But ya never know. I'll switch some around. I want to thank all of you for your help and input. I have been going on other issues that people are having to see if I can help. This is how the world should be, everyone helping one another in a time of need. Just want to say one more thing, I'm checking into why I do not have a 5 volt refrence also. Computer has good power and grounds, but I'm going to go back to basics, something is not right.

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[78f100]

Is the fuse block any good?

The factory fuse blocks get corrosion in them and it causes dome crazy things to happen.

X2
The under hood box is bad about this. You can take it apart and clean the contacts pretty easily.

 

[jsbelectro]

There is one contact in there that melted a fuse. Had to pry it out and clean the terminals. The fuse was for my running lights. I'll look further inside that box and I'll let you know what I find.

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[TyCorr]

Hell, the fuse block in the cab is troublesome. Its circuit layers stacked upon circuit layers. You get some green death in between a layer and its junk.

 

[jsbelectro]

Well I checked every fuse box and all was goid. Went back to basics and checked all my grounds and hots to the computer, checked the relays, fuses, ignition wires, took all the big plugs apart, pulled wire looms looking for corrosion or a short to ground/power, and went to my refrence line that was supposed to be 5 volts, and I barely had 1 volt. Started unplugging sensors on that 5 volt refrence line, and got to the EBPV sensor, and everything came to life. Truck starts and runs. Just need to replace that sensor now. What's bizarre is that having that sensor short to ground actually caused everything to point to a bad pcm. I want to thank everyone for all your help and I will stick around to help any of you when you need it.

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[Arisley]

I forgot completely about that. Had the same exact issue. Truck died going down the road. Unplugged the EBPV sensor and it fired right up. Plugged it it, no start. Drove around for a couple years with it unplugged.

 

[TyCorr]

I forgot completely about that. Had the same exact issue. Truck died going down the road. Unplugged the EBPV sensor and it fired right up. Plugged it it, no start. Drove around for a couple years with it unplugged.

Mine was plugged from the msnifold to the sensor. Had no effect on the truck lol.

I since replaced it and keep it clean now.

 

[Arisley]

Yeah, when the tube clogs it will still run fine. My tube was broken off and plugged up. When the sensor failed, it would kill the truck if plugged in, unplug it, and it runs fine with a soft code.

 

[jsbelectro]

I'll tell you what, that was an expensive sensor. $114 from the ford dealer. Some things you just have to use factory parts for.

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[TyCorr]

They are nuts on prices! But some stuff you gotta bite the bullet, as you said.

 

[jsbelectro]

Some of the part house parts are just bad from the box or they are cheaply built and don't last very long. Truck has been running great

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