Update: Check vavle installed in fuel line--still stumbles @ startup Uggg!

I installed a BMW check vavle in my fuel line. For those new to this topic the backflow valve on in-tank XJ fuel pumps goes bad over time. It casues fuel to leak back into the fuel tank after shutdown. This causes hard starting b/c the fuel pump must now pump new fuel from the tank to the engine. The check valve I installed prevents the fuel from flowing back to the the tank via the fuel sending line. The Jeep still stumbles at startup and continues its hard starting issues. It was a simple install. Man, I thought I had everything figured out. Imagine my surprise when it didn't fix my problem. I'm not sure weather it's a leaking injector, CPS, MAP, etc... Any more ideas?

If you have a stumbling start, check for a cracked header. Mine was cracked, and I fixed it with some ThermoSteel.

Here is a video with different start times showing my quest for a faster starting XJ.

Im having the same issue. I believe that the fuel pressure regulator on the fuel line needs replacing. I read in a thread that someone else had that same problem and a new FPR fixed it for him after he changed all his sensors for new ones.

unfortunately, without troubleshooting some things, it could be tons of stuff, but most likely (after regular tune-up goodies) a problem with the coolant temp. sensor or the air charge temp sensor. This is assuming that it usually fires within roughly three revolutions of the engine and the runs poorly for a few minutes and then gets better (kinda like an older car with a bad choke).

verify that all of your ground connections are CLEAN and tight and break out the multi-meter! If an injector was leaking down, you would likely find a plug that had noticeably more carbon build-up that the others- so try checking/changing them before gettin' too deep into it.

--Shorty

TMXONR said:

If you have a stumbling start, check for a cracked header. Mine was cracked, and I fixed it with some ThermoSteel.

Here is a video with different start times showing my quest for a faster starting XJ.

Click to expand...

I thought your application of Thermosteel wore a hole after time, or did you patch it again and it's been working since?

It did eventually re-crack, so I applied it again using some wire mesh to strengthen it, some of it has cracked off again, but there is enough covering up the hole to allow for better starting now.

In other words, its still cracked but it starts ALOT better.

If it is real cold out side it will stumble slightly, but now that it is getting closer to summer and the temps are warmer it starts fine, it sill cranks a few times, but no stumbling.

I notice mine leaks a little when cool, but when the manifold warms up it stops leaking for the most part (although it will still pop a little if u rev it)

So I guess the thermosteel expands when it gets warm and fills the crack better.

Good enough for me