Hello.
My brother just bought this truck. it is 88 F350 dump truck. It's got 7.5 460 engine. The truck was working fine, and then suddenly it started acting up, we found out that fuel injectors # 2 3 6 7 are not working, looks like they are not getting any electric. We already bought different main CPU, and same thing. please help, what should we check next.

 

I've never had that problem but assuming the computer is good (and likely with 2) I would recommend tracing the wires and making sure that al the connectors are clean inside with no corrosion. you'll also want to follow the wires and make sude they didn;t ment to something like the EGR pipe or whatever other hot parts are looking to short wires. if possible use a test light or meter at the injector connector and at the computer output for the same injector. This way you van verify that the computer is sending the signal, if the computer isn't then it might be some form of safety.

for example on one of my cars I had no fuel pressure or spark, turns out that when the gas is stuck at WOT the computer will not allow the car to start at all.

good luck

 

I would say a short or open in the wiring would have to be the only problem.

Injectors usually all have the same power wire, w/ 12V that just splices out to all injectors. The computer closes(completes) the ground side of the circut when it wants the injector to pulse. Each injector has it's own seperate ground wire that goes to the computer.

I'm pretty sure that all EEC IV systems are bank fire which means it doesn't ground each injector individually, but it grounds, in your case 4 injectors at the same time. It doesn't ground all 4 injectors on the same side of the engine but will split it. I KNOW on a 2.9 it does #'s 1,2,4 and then 3,5,6. I've never messed w/ this on a V-8, but these systems are identical. I've even put 302 injectors in a 2.9! ran a little rich, but it ran! So I'm pretty sure yours is the same, if not someone here will set me straight!

I would think your motor would fire #'s 1,4,6,7 and then 2,3,5,8....sort of like how a dual plane intake works for a carb.

there are all sorts of ways to test the wires, I've even taken connectors apart and grounded the injectors myself to get something running! it works....not well but it works

I would first check to see that you have 12V to EVERY injector w/ Key On, Engine Off. Should be the same color wire on all of them, But doesn't mean it HAS to be.

Next check for continuity between the ground wire at the injector(the other wire at every injector) and the connector that should be resting on the motor somwhere, should connect the injector wire harness to the rest of the engine harness

 

Hi,
I was wondering what your eventual fix was to your 2,3,6,&7 injectors not working. I am having the exact same problem with same motor. I have checked everything and it's driving me nuts. Any help would be much appreciated. Thank you.
Mark

 

Mark, welcome to the forum. It would probably be best to start your own post rather than hooking on to one that's 6 yrs. old. The last activity for alex22 was Sep. of 09. Sorry I can't help with your problem but others may be able to. Good luck and hang in there!

 

Thanks Fuzzybob for the advise. I just posted a new forum 👍