Still missing before warmed up

[theblacksmith]

You may have read my "Dead miss" post. Since then, I installed the FPR blue spring, Turbo Timer and Insight Fuel Pressure Sensor.

Here's my symptoms:

1) Start up Fuel pressure - 77 -79 WOT: 36
2) Until warmed up... still missing/cutting out (only way to describe it)
3) Until warmed up, rev motor to 2000 rpm and, without changing the pedal position, the rpms will drop to 1600 then return, repeats every 6-8 seconds.

4) I can rev engine (before warmed up) to 4K and higher and it will really cut-out.

FICM voltage via Insight: 47.5 - 49


After warmed up, runs great and no 'noticeable' miss. Fuel pressure still high, 77 - 79.

Any suggestions?

Thanks,

[Lilpooh]

Your fuel psi is dropping way too much at WOT.

Here is info on testing/diagnosing your fuel system.

http://napaautotech-classsupport.com...-TIPS-1WEB.pdf

[PGreenSVT]

Try blocking off the fuel return and see if you still loose pressure. If so your FPR is FUBAR even though you have the blue spring in it.

If it still drops with the return blocked you have a fuel delivery problem. Change fuel filters unless done very recently. Do you loose pressure with a full fuel tank? If so I'd replace the fuel pump. If not I'd replace the pickup tube or sump the tank.


Of course you could be dealing with injector stiction as well as pressure issues. Throw a couple of bottles of Rev-X or a quart of Archoil AR9100 or AR2300 in it.

[theblacksmith]

Thanks for the replies.

Actually, the FP at upper end is 80-81.

Since I've never done it, how do I block off return side? Tank is full now and problem exists. Changed filters less than 5K miles ago. Problem existed prior to changing and after changing.

[PGreenSVT]

Cut yourself a disc from a coke or beer can and put it in this nut to block the return flow from the FPR.

[theblacksmith]

Originally Posted by PGreenSVT

Cut yourself a disc from a coke or beer can and put it in this nut to block the return flow from the FPR.

Thanks for the input!
With the return blocked, do I drive or simply rev it up? When it's cold and I rev it high, the motor really cuts out hard. ??

[PGreenSVT]

Drive it and see if you loose pressure under a good load. If so I'd look into replacing the pump.

[theblacksmith]

OK, thanks. I'll give that a try

[mytruckbroke]

I am not debating the diagnosis but I keep a jug of cetane booster because i have run in to a problem here with fuel. Mostly on a couple of my perkins tractors i get a miss under load to the point they will not pull themselves sometimes. When it happens i give it a massive dose of cetane booster from wally mart and in a few minutes of trying to drive it and sloshing it in the tank i am up and running. Have had it happen to my truck but not as severe. When in doubt i dose it with cetane (big dose) if that does not fix it i start looking for problems. Last time it happened i had a tractor pulling a baler that was smoking so bad and missing i thought i had lost a piston. It is cheap and if it doesn't work nothing lost.