limp mode

pdog · 07-21-2008, 03:36 PM

have a 05 duramax ,with edge chip whenever under a load or towing goes into limp mode , with or without chip in the truck . had it to the dealer 6 times they keep bringing up fuel preasure regulator code and egr say they have replaced the preasure regulator and preasure regulator valve ? FRUSTRATED took it to diesle mechanic said same thing and want 2 grand to fix it , hate to spend the money when its still under warentee 2 dealers and after they do there thing , hook up 14 foot motorcycle trailer and it goes into limp mode like clock work check engine light has never come on ! any thoughts ?

GmcLbz · 07-21-2008, 04:04 PM

So it's an Engine limp? Have you change fuel filter?

**BigRedChevy** · 07-21-2008, 09:50 PM

X2 on the fuel filter. Also you may need to shim the fuel pressure relief valve, very cheap mod. Also what level was you running on the edge? If your running one of the bigger tunes you may need a lift pump.

duramaxin14 · 07-21-2008, 10:25 PM

Unstead of shimming it pay the extra couple bucks and put a race vavle in it so much better.

**BigRedChevy** · 07-21-2008, 10:40 PM

The only bad part about the race valve is it won't let any fuel back to the tank. If for some reason you do build too much pressure it has no place to go.

duramaxin14 · 07-21-2008, 10:47 PM

Quote:

Originally Posted by BigRedChevy

The only bad part about the race valve is it won't let any fuel back to the tank. If for some reason you do build too much pressure it has no place to go.

Correct but ive never had a problem with building to much pressure i cant build enough. Fuel will still get back to the tank bye the return line.

Its something like this. if u have a straw and hold your finger over 1 end of the straw and blow into it. When air gets to the end of the straw it will go no where. It will mantain that pressure until it can be realeased. It will not build more pressure because there will always be a steady flow of fuel. And what fuel is not getting used before it gets to the rail will be sent back threw the return line. Its like taking a quick detour i guess. I know i didnt explain to well i will sleep on this and think of a better way to say this in the A.M Or maybe someone will cacth my drift and fill in for me

**IdahoRob** · 07-22-2008, 08:35 AM

What codes are you throwing? Need to know what kind of limp to help you out.

Problem with a race valve is not when commanding rail pressure, the problem is when you are commanding 26,000psi under WOT then you have to lift the throttle. The rail pressure spikes to very high levels, 30,000+. The FPRV will open at this time relieving the pressure, the race valve will not.

With a weak FPRV, the engine limp occurs after WOT when the throttle is released. A shim will stop this problem, but still allow pressure relief at insane levels of rail pressure.