5.0L V8 does not want to start - backfires

[Spdrcer34]

The 1997 V8 in my `92 does not want to start. When it DOES start, after about 2-3 minutes of cranking, it doesn't want to rev. And everytime I try to hit the gas, it pops and back fires on the passenger side....after about 3-4 minutes of idling, warming up, it WILL drive, and have all the power it is supposed to have.

Tonight I replaced the spark plugs, and wires. Almost all of the wires were VERY damaged. Burned through, cracked...you get the idea. The 3 rear spark plugs on the passenger side were wet, and smelled of gasoline. That is the SAME side that I heard the back firing, and popping.

After I was done I tried to start the X, and I got the EXACT same thing, it's like I didn't even change them.

I have Fuel Pressure. 38-40 psi while cranking. I tried starting it with the MAF plugged in, and un plugged. No Change.

I tried to pull the TPS, and swap it out with a known good one, but I couldn't get a screwdriver to bite enough on the screws....

If the TPS is good, I can only think of 2 other things that it could be....the CPS, or the Coils...

Is there a way to test the coils? or the CPS?

Ryan

 

[techieman33]

you could swap the coils side to side and see if it moves to the passenger side, or swap your wifes coil packs in.

 

[Spdrcer34]

She won't let me touch her Mounty!...LOL

I will swap MY coils side to side, and see if that changes anything...

Ryan

 

[techieman33]

She won't let me touch her Mounty!...LOL

I will swap MY coils side to side, and see if that changes anything...

Ryan

lol, it's not like you want to swap the motors to test. I'm practically swimming in extra coil packs here, I have 4 spares right now, let me know if you need some.

 

[Spdrcer34]

Thanks....

I'll let you know...

Ryan

 

[jlsparky7]

Sounds like coils to me.

 

[swetrid]

Look real close at the harmonic balancer, i have seen a few that would be worn and wobble and cause hard starting due to the lose of the crank trigger wheel on the balancer.

 

[Spdrcer34]

Thanks, I'll check that too...

Ryan

 

[Spdrcer34]

I ordered some Screamin Demon Coils from Summit....it was about $5 dollars cheaper than ordering them direct from D.U.I. But I also ordered a couple other small parts too for my Fuel lines

Ryan

 

[techieman33]

Have you confirmed it is the coil packs?

 

[Spdrcer34]

Yes.

 

[Spdrcer34]

I played with the coils, swapped them side to side, and the back firing seemed to swap sides...So I thought I found the problem.

I ordered the Screamin Deamon Coils, installed them today...

...and I have the EXACT same problem.

It takes a LONG time to start the engine. And NOW when it starts it won't stay idling for more than 20 seconds....it cycles from about 750-900 rpms, and bogs every 5-7 seconds, each time bogging a little more than the last time. Until finally it gets to be about 150-250 rpms, and dies. It will fire right back up if I feather the throttle.

I checked the fuel pressure again, and it's about 28-29 psi...I thought it was reading 38-39 before, but obviously I didn't look close enough. When the engine starts to bog down, the pressure spikes to 40psi momentarily before the engine picks back up.

I thought that maybe the fuel filter was plugged, so I put a new one on (I always keep one in stock here at home)....I cycled the key off and on 5 times to fill the filter, and re-pressurize the system. I started the engine, and it had the same issues. So the filter was not the problem.

Now where?

CPS? Fuel Pump?

Ryan

 

[storlied]

[Edit] Nevermind

 

[storlied]

.

 

[mtnlovrs]

With the wet plugs, I hate to say it but... Maybe you have some burnt valves, or intakes that aren't seating. Other than that... TPS or CPS. I can't think of anything else.

 

[Spdrcer34]

I'll order a CPS....I was going to replace it anyway when I re-cam this summer.



Ryan

 

[Spdrcer34]

Anybody else have an opinion on this?

Ryan

 

[techieman33]

I'm baffled by it moving with the coil packs and then it not being them. I was going to suggest maybe it was a bad wire in the harness to the coil packs, but if it moved I doubt that is it.

 

[Spdrcer34]

Im baffled too...

I ordered a Cam Position Sensor. It should be here on Wednesday.

Is the Fuel Pressure @ idle a little low to you?

Ryan

 

[budwich]

I would suggest some compression testing on both side to get an idea of the "mechanical sanity" of the engine.