no spark or fuel

[DWilliamA]

1990 351w AOD Centurion

I mention centurion only because I presume the front half of the truck is actually a crew cab... if that matters?

truck drives like a champ and suddenly on the freeway just turns off.. no fanfare, no lurch or bolt or sound or hesitation.. just ****, off. I was driving OD mode at the time but just easy freeway stuff no heavy load big hills just makes it easy to keep up with traffic speeds, especially because my 33" tires slow me down. On roadside I installed a fuel pump (I have access portal because I just replaced the fuel pump 6 months ago), fuel relay switch and ignition control module.. still no spark at the coil or fuel. I know the fuel pump doesn't work because nothing comes out of it with hoses disconnected. also just the same morning I almost ran out of gas... barely made it to the gas station, but did.

new timing belt 25K ago
new fuel pump and relay 0 miles
newer coil 1k ago
new ICM 0 miles ago

The engine turns over and I get a "Check Engine light"... "Engine light"... and "Battery light" which stay on as the engine turns but the engine light goes off after a second or 2, or maybe its on with key on but goes off when engine turns something like that.

can not pull any codes either.. nothing

clues maybe

I have had to replace the wiring harness at the transmission, the wires look ok but I wasn't too smart and wrapped them in electrical tape and tried to wrap again with an aluminum heat shield thing, but the tape melted anyway so I can't actually see the wires, but they are not exposed and corroded like before .. What the truck has been doing very recently is going into limp mode when cold... after 5 minutes, 10 minutes tops it comes out of limp mode and drives normal.

could it be ignition switch please ... ? or main computer (ECU? or EEC?)... There is talk on google searches about a ICM fuse... but my fuse diagram mentions nothing about an ICM fuse - still doesn't explain the fuel pump though does it?

Help - ideas?
David

 

[Tiha]

I think you are on the right track with fuse, ecm issue. Pretty strange.

Is this a half ton? Or 1 ton? There are some slight differences in bronco/f150 wiring compared to the F350 crew cab stuff.

Either way probably start with a test light.

Attached is the wiring diagram for the 1990 (supposedly because being Centurion it could be an 88 or 89 that sat around waiting to be converted)

Centurion also did some shady wiring.

Since the engine turns over that kind of points us away from the ingniton switch for now.

Lets start on page 12-44 (see attachement)

Upper left corner.

With a test light, checking power on the EEC relay. (out under the hood next to the fuel pump relay and diagnostic connector)

The yellow and Red with light green stripe should have power on them.
(red with light green comes from ignition switch, test with ignition switch on)

Well, lets start there because it gets a little crazy after that. But not having voltage on both of those wires with the key on will not run the ECM or Fuel pumps.

 

[DWilliamA]

it is a half ton C150... contrary to popular belief they did make 1/2 ton centurions... I have owned 2 of them both 1990

 

[DWilliamA]

btw... what is this for.. its been burnt out for at least 15 years..

 

[DWilliamA]

so the red/green is throwing 11.65 volts key on ... and the yellow is throwing .04 volts key off

I am actually checking the ECR relay.. not the EEC... the ECR has yellow and red/green wires.. the EEC doesn't... so I assume you meant to check the ECR.. the EEC is what I plug my OBD1 in to... do have this correct.??

 

[Tiha]

Ok. Page 12-42 of the manual, upper right corner, starter relay, says the yellow should be 12v all the time.

It is a 20 ga, blue with white stripe fusible link.

Sounds like a bad fusible link from starter relay on fender.

Should be able to jumper that yellow wire direct to 12v, to test, adding an inline fuse, or new fusible is the best.

 

[Tiha]

btw... what is this for.. its been burnt out for at least 15 years..


View attachment 31133

Honestly cannot tell from that picture. Maybe someone else will know.

Was gonna say EEC data connector but I think the wire colors are wrong.

 

[DWilliamA]

I am checking the square relay

 

[Tiha]

Looks like the correct one. That should be the EEC relay and the fuel pump relay looks like it is laying right there as well.

I should know what that burnt up connector is, but been too long, can't remember. Hopefully someone else will pop in and clear that up for us.

 

[DWilliamA]

Ok. Page 12-42 of the manual, upper right corner, starter relay, says the yellow should be 12v all the time.

It is a 20 ga, blue with white stripe fusible link.

Sounds like a bad fusible link from starter relay on fender.

Should be able to jumper that yellow wire direct to 12v, to test, adding an inline fuse, or new fusible is the best.

attached is photo of starter relay... there is no blue/white wire.. but the green wire looks to have a fuse link in it, which could be blue whi

Ok. Page 12-42 of the manual, upper right corner, starter relay, says the yellow should be 12v all the time.

It is a 20 ga, blue with white stripe fusible link.

Sounds like a bad fusible link from starter relay on fender.

Should be able to jumper that yellow wire direct to 12v, to test, adding an inline fuse, or new fusible is the best.

well I'll be... you can see the little copper wire burnt broken in the photo attached and the cover is blue.. dirty so I can't see a white stripe but sounds like this is the culprit .. next questions will be how to exactly jumper this.. electricity is not my cup of tea and I need to fix this fast at least temporarily... I have an employee in the lurch waiting for my work truck... going to study the ends of this wire some more... and think some.. wire-12v fuse-wire... but jumping the link with fuse won't use 20g wire... so match the yellow.. but I see a bunch of these little fuse wires... I need to go look closer, not sure what I am looking at yet.

 

[DWilliamA]

attached is photo of starter relay... there is no blue/white wire.. but the green wire looks to have a fuse link in it, which could be blue whi



well I'll be... you can see the little copper wire burnt broken in the photo attached and the cover is blue.. dirty so I can't see a white stripe but sounds like this is the culprit .. next questions will be how to exactly jumper this.. electricity is not my cup of tea and I need to fix this fast at least temporarily... I have an employee in the lurch waiting for my work truck... going to study the ends of this wire some more... and think some.. wire-12v fuse-wire... but jumping the link with fuse won't use 20g wire... so match the yellow.. but I see a bunch of these little fuse wires... I need to go look closer, not sure what I am looking at yet.

photo of culprit wire... it has 3 fuse link wires in a bundle ... not sure how to go about fixing this fast ... don't even know if local auto parts stores sell this wire even

 

[Tiha]

Correct you are going to want to splice to the yellow wire, getting rid of the blue fusible link all together.

An inline fuse holder like in the attached picture is available at most parts stores. Probably use a 20 amp fuse. More than enough current, but still offers protections.

I would put an eyelet on one end and attach to the starter relay, then butt connector on the other end to the yellow wire.

 

[DWilliamA]

so I spliced in fuse link like photo.. soldered connections, had to do all three wires that shared that one main yellow wire..... still no power to the yellow at the relay.

I replaced the relay too while I was there.

 

[DWilliamA]

put some 20 amp fuses in... still no start. the check engine light does not come on now, I do not hear the fuel pump coming on with key on for a couple seconds and it still does not engage the obd1.. reads nothing.

I do have 12.5 volts at the yellow wire at the relay... been charging my battery so it went up.

no spark at distributor coil wire

 

[Tiha]

Hopefully that is progress.

Now we need to check for voltage at the igniton coil, or ignition module or distributor.

Upper right of page 12-45
Red with lt green stripe.

With key on, you should have voltage at the all 3 of those.

I would be starting to suspect the TFI module.

I think Motech said if you remove the SPOUT connector and have spark that points to the PIP module. Sounds like an easy thing to check.

 

[DWilliamA]

Have volts at red lt green at dist

Took out spout and it starts runs.. but it doesnt rev up at first like it always does when cold.

Put spout in and it starts runs.. I think it reved up at start.. but I had it idling for a minute or so without spout in so I may have warmed it just enough..

The only thing I did since last night was take out the ECU to get #'s to order .. which I did... think I will keep it just in case.. and there was a wire to the transmission that melted but not fried... know this... I had a bunch of thermactor issues while back and turns out the thing that I think blows cold air into the cat convert... or sucks hot air out ?? Wasnt working and my cat convert or pipes in the area were running real hot which melted the wiring harness and fried some wires eventually.. I rewired but the aluminum sheild I put in didnt sheild so good and a couple wires got melted.... maybe that tranny wire disconnected the tranny which tripped the ECU into no start mode?? Seems wild to me... in any case that happened. And recently this last week my truck goes into limp mode when cold buts comes out 5 - 10 min later once warm.. it still goes into limp mode when cold... seem like another issue not related to the no start issue?

 

[DWilliamA]

about the fuse link wires... those wires were squished into a space where the battery cable was rubbing on them.. and my battery isn't strapped down...so it probably rubbed and wore... if this wasn't cause then I am left wondering why did one of them blow? going to assume it was the cable rubbing for now.

And ... huge thank you for walking me through this.. I never would have figured this out on my own.

 

[Tiha]

Glad you got it going.

Wires rubbing on the fuse link it quite possible. Also could be one of the other melted wires you are referring to, they could have shorted and popped the fuse link. But now you have a inline fuse that is easy to check and replace if it happens that way again.

 

[Motech]

What the heck is this wire here?



That is the STI, or Self Test Input connector for scan tool diagnistics. There should be nothing attached there whatsoever until a scan tool is plugged in.