Not entirely sure what THAT is, but the fuel pressure regulator is what prevents "fuel pressure spikes" and on your year, it is in the pump itself and in the line, I believe. I do know there is NOT one on the rail itself though.

95 & down had it on the rail, and it was right where the fuel lines (pressure and return) plugged into the rail.

 

looks to be the Fuel Pressure Dampener it does exactly what you said sir, it prevents fuel pressure spikes lol. it normally works in conjunction with the FPR.

 

Are the spikes coming back up through the injectors to the rail? Why doesn't the new one have it?

 

Hmm... never heard of one being in the middle of the rail away from the fuel inlet. But, I'm not real familiar with the OBDII stuff either.

 

Another one for you experts. The sound is clearer in the first 10ish seconds, my guess/hope is the torque converter bolts are loose? It's weird though the sound changes when I move the transfercase lever.

 

^very hard to tell from the inside, if possible get a video from underneath the sound would be more audible.

 

I'll try. I only notice it now and then. I think it's only when in gear idling. I'll try to check the torque converter bolts tonight or this weekend. Just looking for ideas if that's not it.

 

Yep that's a fuel pressure damper.

1987-1996 (early '96) used a system with an unregulated fuel pump, vacuum FPR on the rail, and a return line from the rail back to the tank. In this system the FPR nominally regulates pressure coming in from the pump. Fuel injectors open and close and will use whatever fuel is passing by - any fuel unused by the injectors is just returned to the tank.

Starting in mid/late '96 model year, the new OBD-II setup is a returnless fuel system with the FPR located in the tank as part of the fuel pump module. The pump pressurizes the entire system, and fuel stays up in the rail until it is used. (Ask someone with heat soak how much they like that 'feature' lol)

The problem with this setup is that fuel injectors are not nice smooth loads. They suddenly open and then slam shut. The opening causes a very brief drop in pressure in the rail, and the shutting causes a spike. Another issue is turbulence caused by hydraulic shock - plumbers know this as water hammering. Basically the same thing that happens when you open a tap in your house all the way and then turn it off abruptly (that loud bang) happens in the fuel rail every time an injector is fired. Because of this the 1997-1999 fuel pressure spec is something like +/- 3 PSI.

Starting officially in 2000 model year (although my '99 XJ had one) Chrysler threw in this very simple damper. The idea is that it dampens these shocks, and being a nice springy diaphragm, lessens the drop in pressure, too. Fuel pressure spec for 2000+ 4.0L is only +/- 1.5 PSI. It's possible this is one reason that the 2000+ makes a couple more ponies on the high end.

 

Sounds like a classic case of loose TC shift linkage.


If you push forward on the shift handle and the rumble stops it is the loose linkage problem.


Chrysler sold (past tense) a kit to fix this but no longer does. Crown Automotive sells an aftermarket kit. I bought one but didn't use the sheet metal screws included in the kit, I reused the original machine screws.


http://www.ebay.com/itm/331483790973

 

Just had to take off my belt to replace something. I put it back on and now at start up there is a squeal that last not even half of a second. What did I do? Over tighten the idler pulley?

 

Probably didn't tighten the belt enough

 

or he can eliminate the stock complex linkage and go with the boostwerks engineering simplified linkage.

http://www.boostwerksengineering.com...ans-_p_25.html

 

Does it make a difference on a 242?

 

It might, i'd email boostwerks and ask. i paid $53 for my linkage shipped to Capac, which is near Port Huron.

 

Yes, and it's a different product listing