Electrical Gremlins

[rusty ol ranger]

What do you make of the eec showing a huge decrease in voltage st pin 22 between KOEO and KOER?

I’ve done what you said many times, with two sets of injectors (one remaned and one cleaned and checked for function and spray pattern), hoping for a different result each time. Nothing. Exact same symptoms. I suspect that my fpr has failed internally as even priming many times won’t get my pressure up to 42 psi. That is supposed to be the preset spring tension in the fpr, yes?

There are two things I haven’t done yet. One is to throw on an old regulator with the return line capped to see if it will then hold after priming. That isolates the rail and high pressure check valve. The other is to hard line the fuel pumps with 12v to see if the changes it’s behavior. But again it seems I have two issues here. Unless the readings I’m getting from the computer check out?

Listen to @RonD for the finer points of the ECM. Im far from an EFI guru. My speciality has a choke and idle screws lol.

If the FPR has failed there will be fuel in the vacuum line running between it and the manifold

 

[aball4620]

Pull out the Computer and open it up, its out of warranty, lol

Look at the 3 blue or black capacitors, blue ones seen here: http://www.auto-diagnostics.info/ford_eec_iv

These go bad and leak after 20-30 years, not hard to replace, 1994 and earlier computer this is 99% of why they start to "act funny"

Just did this on my 1994, cost $5, back to normal
Mine had 1 that was obviously bad, broken wire, but 2 were actually bad/broken, of course, replace all 3

Man, pulling apart circuit boards is not something I’m super experienced with. Too bad the warranty is expired Is this the part you’re referring to? I’m only seeing a single example on this board. And with the demise of radio shack is there another place I can walk in and ask some questions or is this an Amazon pickup?

 

[aball4620]

Listen to @RonD for the finer points of the ECM. Im far from an EFI guru. My speciality has a choke and idle screws lol.

If the FPR has failed there will be fuel in the vacuum line running between it and the manifold

That's always been my understanding as well, and that is not the case here. No gas in the vacuum line. But I’ve also come across people saying it can fail in either the spring or the diaphragm, with the former “leaking” through the return line and the later sucking into the intake. Is that correct?

 

[rusty ol ranger]

Yes thats the part.

But that ECM looks good.

 

[rusty ol ranger]

That's always been my understanding as well, and that is not the case here. No gas in the vacuum line. But I’ve also come across people saying it can fail in either the spring or the diaphragm, with the former “leaking” through the return line and the later sucking into the intake. Is that correct?

The return line goes straight back to the tank. Usually it leaks into the vacuum hose then is sucked into the manifold.

You can pinch the return line off and make see if it helps.

 

[rusty ol ranger]

88 wouldnt still have a seperate canister filter would it? Anyone know?

 

[aball4620]

No additional canister filter. Just the inline and the socks on the tank pick ups. Plural because this is an elusive dual tank.

 

[rusty ol ranger]

No additional canister filter. Just the inline and the socks on the tank pick ups. Plural because this is an elusive dual tank.

The F series switchers had a bad habit of getting stuck inbetween tank settings....and all, or a good portion of, your fuel ended up in the other tank instead of the combustion chamber.

Have you explored this?

 

[aball4620]

The F series switchers had a bad habit of getting stuck inbetween tank settings....and all, or a good portion of, your fuel ended up in the other tank instead of the combustion chamber.

Have you explored this?

I have, that happened already and blew out two new FPRs before I figured out what was happening. The slider valve on the return line had frozen in between the two tanks and was creating massive back pressure. I was getting 65 or so at the rail. This is what started the entire saga because it managed to blow out an fuel injector o ring on cylinder 6. I sourced a new one that was after market and didn't fix the delivery issue. So I got out my multimeter and tapped into the upstream and downstream wires going to each tank. I was getting super erratic voltages with KOER, like oscillations between 0.5v and 6v constantly. So they send me another. Similar issue. Hardwiring the lift pumps and cutting out the tank selector interface did not change anything. Returning to a gas can before the selector valve did not change anything either. Prior to the catastrophic failure I had been running rich for a long time and couldn't figure out why. Everything that was obvious had been gone through. As soon as I changed the selector valve it was no longer blowing gas out the tail pipe and it seems the selector valve was half failing for a long time causing more fuel to dump into the cylinders. But, this didn't change the rough idle with hunting and stumbling. Or maybe just a tiny bit but not enough to call it a win.

 

[aball4620]

I have, that happened already and blew out two new FPRs before I figured out what was happening. The slider valve on the return line had frozen in between the two tanks and was creating massive back pressure. I was getting 65 or so at the rail. This is what started the entire saga because it managed to blow out an fuel injector o ring on cylinder 6. I sourced a new one that was after market and didn't fix the delivery issue. So I got out my multimeter and tapped into the upstream and downstream wires going to each tank. I was getting super erratic voltages with KOER, like oscillations between 0.5v and 6v constantly. So they send me another. Similar issue. Hardwiring the lift pumps and cutting out the tank selector interface did not change anything. Returning to a gas can before the selector valve did not change anything either. Prior to the catastrophic failure I had been running rich for a long time and couldn't figure out why. Everything that was obvious had been gone through. As soon as I changed the selector valve it was no longer blowing gas out the tail pipe and it seems the selector valve was half failing for a long time causing more fuel to dump into the cylinders. But, this didn't change the rough idle with hunting and stumbling. Or maybe just a tiny bit but not enough to call it a win.

I should say that now it feels like it is running lean. Before changing that valve it was dumping gas (I had about 18 months of 8-11 mpg). Now it feels like it is struggling to get a full combustion from the other direction - not enough gas.

 

[rusty ol ranger]

I should say that now it feels like it is running lean. Before changing that valve it was dumping gas (I had about 18 months of 8-11 mpg). Now it feels like it is struggling to get a full combustion from the other direction - not enough gas.

Pull codes.

Im wondering to if you got excess carbon on the intake/valves thats causing some of these issues as well from the rich burning.

 

[rusty ol ranger]

Oh wait you did pull codes already didnt you?

Im wondering if your chasing the wrong system at this point and you got some weird Ignition module/distributor issue

 

[aball4620]

Oh wait you did pull codes already didnt you?

Im wondering if your chasing the wrong system at this point and you got some weird Ignition module/distributor issue

Correct, pulled codes. The only thing that comes up is 63 in continuous memory KOEO, which is the TPS voltage out of range. When I checked pin 47 for identical voltage changes a couple days ago is when I finally started this thread.

New distributor, new module, new heads with new valves. But when I upgraded the distributor it didn't change anything so I swapped the old and new again just to make sure. When I blew the injection seal I decided to finally upgrade the heads as I think I had a small crack that was behaving a bit like a head gasket leak. 88 was the last year the heads tended to crack around the rocker arm bosses, so upgraded to new - not re-maned - heads. But please keep the "what about this" coming, because I've been at a loss for a while now.

 

[aball4620]

My father's suggestion has, and continues to be, to rip out the EFI as violently as possible and install some Webers. I'm not 100% in disagreement, but damnit I would rather just find the (likely) one thing that is handicapping this thing.

 

[rusty ol ranger]

My father's suggestion has, and continues to be, to rip out the EFI as violently as possible and install some Webers. I'm not 100% in disagreement, but damnit I would rather just find the (likely) one thing that is handicapping this thing.

Converting a 2.9 to carburation is very expensive and tricky thing to do.(No 2.8 parts dont really work) Trust me i checked into it when i fought mine for a year before finally figuring it out.

Im stumped at this point though.

Ill summon the big guns..

@RonD @adsm08 @PetroleumJunkie412 @fastpakr