I was wondering if you guys could help me out here. The past couple of weeks my truck has been running like AS* on and off.
And yesterday she started running bad and it stayed that way. It feels like one of my cylinders is not firing. First I checked all the plugs and all are running fine except #1 cylinder. It was black and fouled out. I then changed the spark plug wire and spark plug and made sure it had spark. The spark checked good, No problem there.
So then I let it run for a couple mins while I wiggled all sorts of wires and sensors. And then I noticed a heavy fuel smell coming from the exhaust. I looked down at the passenger side tailpipe and saw some light bluish smoke coming out w/ a heavy smell of unburned fuel. (It was almost like I was down at the race track w/ that fuel smell that makes your eyes water)
So then I thought......GREAT! cylinder #1 is shot.
I then did a compression test on all cylinders. All of them including #1 were at 150 psi. + or - 5psi.
So the next step (I think) is to pull the #1 cylinder fuel injector. Any thoughts guys? They would be greatly appreciated.
*1991 5.0L w/ 24# Ford Motorsport Injectors*
Jerry D.

 

The next test is to check the fuel pressure. You need to attach a guage to the schrader valve, and observe what the pressure is running, and then disconnect and plug the line going to the regulator, and observe what the pressure is. Then, and this is the most important part, turn the engine off and observe what the gauge does. It should remain rock steady for several minutes or more. I suspect, however, that you will see the gauge drop fairly quickly. I'm guessing from your description that the injector to the number one cylinder is not closing all the way, which is flooding that cylinder, and eventually fouling the plug. And, if one injector is bad, the others are likely compromised as well, at least to some degree.

To be sure, when the engine is cold, turn the key on and off several times, allowing pressure to build up, and then go pull the number one spark plug. If it's wet, your injector is leaking.

 

Thanks,I'll check those out!
A buddy of mine that owns a speed shop is gonna lend me a 24# injector just to see if that is the problem.
I'll keep you posted on how I make out. I hope this is it!

Jerry D.

 

Well, No luck today, even with the new injector.
I went over everything again, spark (cap rotor plug wire),compression [150 psi),and fuel......
Now, I'm not getting any fuel to the #1 cylinder!
I checked the resistance on the injector. I think it was like 5 ohms. It's gotta be the injector wiring harness, or the computer.
I checked the harness for any shorts.....nothing!
I even turned the ignition on and checked the voltage to the injector plug, and I'm getting power.
Does anyone know what the voltage should be?

Any other thoughts guys?

 

DO NOT RUN THAT INJECTOR YOU WILL FRY YOUR COMPUTER!!
That is the wrong impedance, the correct value is about 13.5 ohms. Don't screw around wiith it, simply test to see if the fuel rail is holding pressure like PKRWUD said. If it's leaking, and it probably is replace the leaking injector with the correct one

 

Strangeranger, you right my injector ohm reading was 14.1
I wasn't sure last night when I posted. Sorry for the confusion.

Well, today I went and bought a noid light. It works like a charm!
It told me that my #1 injector plug is not getting any pulse.
So, I ordered a remanufactured computer. It should be here Monday. I'll keep you posted.

One other quick question. When I ordered the new computer I used the code on the side of the computer (A3M1)
I know this isn't the stock computer number for a 1991 F-250 w/ 5.0L. Being that I converted over to massair. A new computer came w/ the Ford massair kit. I was just curious if anyone knew what vehicle that code is used for?

 

Did you check the harness for continuity? Youre going to be very pi$$ed if you went and bought a new computer and the only problem was a broken wire.

 

Yeah, I hate it when that happens.

 

I had the whole harness off and looked real good for any breaks cuts or kinks.
Every connector except the #1 had resistance. It was open.
But then again, all the connectors except for the #1 have three wires going into the connector. The #1 only has 2 wires going into the connector. Which makes me think it is grounded by the ECM. Am I making any sense?????????? Bare with me here.

Jerry D.

 

I've never seen an injector in a small block Ford with 3 wires going to it.

 

The setup I have is the Ford Motorsport massair conversion kit part #FMS-M9000T50

http://store.summitracing.com/partde...FMS%2DM9000T50

 

Doesnt that kit use 2 of the factory wires for two of the injectors?

 

The one I have uses 8 new injector plugs. It also comes with 8 stop plugs to install into the old stock harness.

 

That harness only has plugs for 6 injectors. I don't get it???

 

I heard somewhere that that kit uses two of the original wires to fire two injectors, since the speed density system is bank fire, then includes a harness (like in the picture) with 6 new plugs for the remaining injectors because the MAF system is sequential firing. then you cap off the 6 old plugs and forget em. but it sounds like dvldog458 has a bit different system.