Hey guys, it's been a while since I've been on here; good to be back!

So, we went to start the 5.8L '88 F-250 the other day and after cranking it for about 6 consecutive times around 7 seconds a pop and hearing it start to fire it finally started up and was running, but not running well. We rev'd it up a few times and it was idling, but not well, it was missing pretty bad. We shut it down and moved the car out of the way and when we tried to start it up again it wouldn't fire at all unless we added some fuel into the intake. I checked the voltage to the injectors and it was jumping to 12V off and on while trying to start which I assumed was normal, I opened the valve on the fuel rail to see if we had fuel pressure and it seemed to pump out plenty of fuel. And of course I checked to see if there was consistent spark which there was (of course because it will run with fuel in the intake).

So we have fuel pressure, spark, and voltage to the injectors...what would be the next thing to look at that would keep this truck from starting up?

A little background on the truck..my dad got it cheep and a previous owner had torn just about everything off the engine that he didn't think it needed...I don't think he did a lot of thinking. I might take a picture and post it up for you guys to get a laugh out of it.

Anyway, thanks for reading, hopefully someone can shed some light on this latest conundrum! You guys Rock!

 

The Computer.

 

Leaking fuel injectors,
Plugged fuel injectors.

I'm not sure if a stuck IAC would cause a no start condition but its easy enough to clean an test.


How long has it been sitting? (ie - how old is the gas thats in the fuel rail?)

 

Thanks for the replies, the reason why I didn't think that the computer had given up the ghost is because the injectors are controlled by it and there is voltage going to them. Is it possible for the computer to only partially go bad? And if so, how would I test it to see, and what parts that would otherwise be controlled by the computer would keep the engine from starting given that we have fuel pressure, injector voltage, and spark?

I can't imagine that all of the fuel injectors would have suddenly become plugged after working just 5 minutes prior so I'm going to rule that one out, and if they were all leaking wouldn't the engine still try to at least fire?

As far as the idle air control is concerned, I don't know why that would keep it from starting all together but I suppose it's possible since I don't fully understand the extent to which it controls air intake. Can it cut off the intake completely even at WOT?

As far as the gas is concerned, the truck was running just about 5 minutes prior to the last time we tried getting it to run and when I opened up the valve on the fuel rail it looked pretty clean..plus we added some new gas to the tank so I don't think that's the problem.

The mystery continues...any more help would be great, thanks again guys!!!

 

The computer has nothing to do with voltage going to the injectors. That is controlled by the Power relay and it is controlled by the Ignition switch.
The computer only grounds the injectors to fire them.

 

And without the ground you would have no voltage. The computer controls them by regulating their ground lead. The B+ lead is a constantly closed circuit when the ignition switch is in the on position.

 

With out the ground from the computer you would have no current flow.
You would have voltage on both sides of the injector with and open ground from the computer.

 

I suppose that I could argue the technical definition of voltage right now, but that is neither here nor there...Wouldn't you agree that the injectors are in fact controlled by the computer alternating their ground? I think you would because that is how they work. And since the EEC is alternating the ground to the injectors wouldn't you also agree that at least that part of the EEC is still functioning? It would be a stretch not to...soooo, doesn't the gist of my original reply to you still stand?
You can just subtract the voltage part if you like: Here is a quote from my original post that should have shown that the computer was still controlling the ground: With that said, I'm really not trying to start an argument about semantics here, I'm just trying to uncover the reason why the truck wont start. Sorry if I unwittingly offended anyone.

I am however still thankful for the replies and the attempts to help.

 

I did not see that in your fist post however the voltage to the injectors should not be going off and on. It should be on all the time. I think you mean the the ground side of the injectors to the computer are going off and on.

Sounds like a fuel pressure problem, get a gauge and put it on the fuel rail and ground pin #6 of the EEC self-test connector and see if you are getting about 45 PSI pressure.
Anything below about 28 PSI will not start the engine.

 

Sounds good; my understanding of voltage has to do with difference in electric potential, so without a ground there is no difference and therefore no voltage. I just need to look at it from a different angle I suppose.

We will try that, I guess everything has to go bad at some point. That would be the first place to look.

Any more ideas are welcome. Thanks again!

 

Ok, so we picked up a fuel pressure tester for $10 from Harbor Freight..with the ignition turned to the on position it pumps right up to 40lbs and while cranking it averages around 24lbs. It has spark and while we were cranking I attached the multimeter to the leads coming from one of the injectors and it makes it to around 5 volts off and on.

We got it to crank a couple times but it wasn't running strong enough to run in gear; after that it wouldn't crank at all.

So, my next questions are: does the EEC add resistance to the ground to drop the voltage leading to the injectors? How long is power applied to the injectors each cycle at idle?

Newbie questions: Where is the EEC in this truck and where is the test plug?

Thanks again for all the help guys..this thing hasn't won yet!

 

We're going to revisit getting this truck started and running now that we're nearing completion of the suspension repair on the other truck.

So, we have spark, fuel pressure, and opening injectors..what the heck would keep it from starting up at this point? Where should we look first? I can't remember where I was reading about how to read the codes from the test plug...and my newbie questions still stand:

Newbie questions: Where is the EEC in this truck and where is the test plug?

If anyone could help out with this conundrum we would be very grateful!!

 

I think on an 88 they in the same place as in the photo below.
For the code reading goto:
http://fordfuelinjection.com/?p=13



/

 

Awesome, thanks!! You have been an invaluable help!

 

Ok, so we were able to get the truck to start but just barely..I read the codes off of it and they are as follows:

First set: 21, 81,82,85,84,95
second set: 14, 31,41,51,63,95

What we are wondering is what codes we should tackle first just to get it running..then we'll go through one by one fixing the others.

I took some pictures of the wiring nightmare that will hopefully shed some light on things (sorry, my good camera is in Tampa)..

It's hard to see, but the wires leading to this device are mostly bare just before they enter the plastic. When disconnecting it it doesn't seem to affect things too much.



This plug was actually loose, the clip is broken on it. We think it is the reason why it just simply wouldn't start at all...when we press it in and mess with it a bit we are able to get the truck running(just not well).



This fusible link's wire is severed, but while I was typing this my dad thinks he has discovered that it leads from the ignition and powers the distributor..or something.



So that's all she wrote for now...if anyone could give us any help it would be greatly appreciated! Thank you all so much!