Cylinder #8 Misfire - Questions

Rob D · Jul 18, 2016

So I have searched all around the web on this problem.

2001 F350 ZF6. Truck does not have any loss of power, it does not shake or have any bad shudder etc., a very slight vibration at idle- my prior 03 7.3 felt the same way at idle. Truck does not smoke at all, and from what I can tell has never had a chip on it. This thing is a cream puff. Truck did have a 5er hitch so I am sure it did some work earlier on in it's life.

Before I bought the truck I had it gone over at the local shop. Buzz test was fine, contribution test was fine. Tech cleared the P0308 code and agreed truck did not appear to be missing at all. The SES light stayed off for about 100 miles, then SES came back on with same code. 180K on the clock.

From what I have read it comes down to either:

1 - Bad Injector
2 - Bad harness
3 - Bad CPS
4 - Bad fuel filter

Working from bottom up as those are easiest and cheapest to repair I have found that the upgraded CPS did not fix the problem. I did read auto vs manual has different parameters for what will throw the code if the CPS is slightly off (but could not find the thread again).

Checked the fuel filter this weekend and it was gross, definitely neglected. There was a decent amount of crud at the bottom of the bowl - I cleaned it all out. My concern is that if the main filter was this dirty, the tank is probably in lousy condition too. How often is it recommended to drop the tank and service the filters/socks in the tank? Also would it hurt anything to open the drain valve on the bowl with the truck running as a way to get as much fuel out of the tank as possible?

I have new filter on order, as well as upgraded regulator spring. I also read that removing the plunger/spring inside the tube that the filter goes over removes unnecessary restriction - obviously would never run the truck without a filter...hoping new filter and increasing pressure a bit with upgraded spring, if the #8 is starving from fuel a little bit this will fix it and maybe take care of the code?

Thanks in advance
Rob

Arisley · Jul 18, 2016

Google Hutch and Harpoon mod. Something that should be done to all 7.3's.

Pull the valve covers and check the UCVH. The harness that supplies voltage to injectors and glow plugs. They are very prone to going bad. Usually not intermittent though.

Rob D · Jul 18, 2016

Arisley said:
Google Hutch and Harpoon mod. Something that should be done to all 7.3's.

Pull the valve covers and check the UCVH. The harness that supplies voltage to injectors and glow plugs. They are very prone to going bad. Usually not intermittent though.

Thanks - I did come across the Hutch mod but from what I could tell it looked like the hutch mod just eliminates the mixing valve with the internal filters in it and then replaces with an external pre-pump filter?

I like the idea of this but is it really necessary for a truck that is going to remain stock? This truck to me is just a house truck and I am not trying to dump a bunch of money into it. Factory setup has lasted 15 years at this point. If I planned on doing injectors I would definitely do the mod?

Arisley · Jul 18, 2016

Yes, it is worth it, in the tank one time. Those filters get really clogged. You also move the return line as far from the pickup line as you can. Return fuel is aerated. The stock system mixes return fuel with new fuel. So you are getting warmer aerated fuel to you injectors. The pre pump mods gets nice cool clean fuel to the injectors.

Rob D · Jul 18, 2016

Alright - if doing all the work would you recommend to just go to a fass while system is apart?

dsberman94 · Jul 18, 2016

dmd · Jul 18, 2016

The mods made a difference when my truck was stock. Noticeably more quiet.

TyCorr · Jul 18, 2016

dsberman94 said:
No.

What fuel system do you have?

dsberman94 · Jul 18, 2016

TyCorr said:
What fuel system do you have?

Thank god not a fass. Plans for riffraff draw straw and 6.7 hfcm. Stock is more reliable than fass by a long shot.

TyCorr · Jul 18, 2016

dsberman94 said:
Thank god not a fass. Plans for riffraff draw straw and 6.7 hfcm. Stock is more reliable than fass by a long shot.

What one do you have?

To the op if you have someone local who will warrantee the fass and its plug and play outside of maybe running better fuel lines do it. You get pre and post pump filtration. I bought a walbro fuel pump and I have a full fuel system. I was told "the walbro is junk. Dont use one". I bought a fuelab pump three months after and the walbro is still going. Holding 60psi with 250/200s.

I recorded some videos this weekend with my truck sitting idling with 250/200s and NO CHIP and its better than 90% of the trucks Ive heard. Thats why Im asking Berman what fuel setup he has becausehe us talking out his azz. Yean we've all heard about how crappy fass is but walbro is too and ive gotten years and miles out of mine.