Author Topic: how to relieve fuel pressure (Read 3475 times)

monty23psk · « **on:** March 04, 2013, 06:58:40 PM »

I have the Haynes manual and the e36 manual states to use the Sch. valve which is not on the e30 m42. Just want to know how others have done it. Of course remove the hose is another way.

TIA

Nelson_40 · « **Reply #1 on:** March 06, 2013, 10:28:00 PM »

Surprised no one chimed in with a helpful tidbit. As for me I just yank the line. But I rather enjoy the smell of gasoline. Still, there must be another way.

MLM · « **Reply #2 on:** March 07, 2013, 01:06:04 AM »

pull pump fuse and crank engine?

monty23psk · « **Reply #3 on:** March 07, 2013, 10:01:34 AM »

That's how the Haynes manual states it.

deansweet · « **Reply #4 on:** March 07, 2013, 12:02:14 PM »

Quote from: MLM;120760

pull pump fuse and crank engine?

x2.

DesktopDave · « **Reply #5 on:** March 07, 2013, 04:48:17 PM »

I pull the fuse as well - though you could pull the relay as well, it's easier to get at sometimes.

monty23psk · « **Reply #6 on:** March 08, 2013, 08:53:14 AM »

I pulled the main relay and very little fuel came out while installed my pressure gauge. I hold a constant 38-40 psi. I find this low as we use a 3.0 bar FPR, which equates to a little of 43. The bad thing is that when I turn the car off, it immediately drops to under 10 psi and within 5 seconds or less, it is at 0. This could be the check valve in the FPR or fuel pump or another leak like injectors. I am going with the FPR as I am running rich. This is the reason for testing the fuel pressure. Also it is 22 years old so I will change out the cheaper/less time item first. Next will be the injectors to the 4 pintle version. Last will be the fuel pump unless it looks to be the fuel pump after the FPR swap.

lars318is · « **Reply #7 on:** March 08, 2013, 12:14:06 PM »

I pull that small vacuum hose that leads from the side of the throttle body to the FPR. When I loosen the hoses, there is still fuel in the lines, but it is not pressurized.

monty23psk · « **Reply #8 on:** March 08, 2013, 01:11:13 PM »

From my readings, if there is fuel in the lines, FPR is bad. Should only be air, which mean internal diaphragm is shot and letting fuel through.

monty23psk · « **Reply #9 on:** March 13, 2013, 04:27:28 PM »

Just wanted to give an update incase someone searches this post for their issues. I swapped out the FPR and all seems to be good for the moment. My DME codes went away, only a 1444, no more 1222 or 1215. Also idle is better. Only vibrates alot due to e28 engine mounts, and even better if I have the AC on. I guess the extra load helps. I see have to see my MPG as I had to refuel today and filled up the take. I hope to see better than 25mpg. The vacuum hose nipple on the FPR had little drop of gas. This means that gas was getting into the intake side and causing the running rich issue which then caused the O2 to go into a loop and give me the lumpy idle. This is what I think, at least. I had to refuel, so filled the tank, reset the odometer and lets see how it goes. If MPG does not improve, I will check the FPR again to see if I still have a leak. Next then will be the injectors, which I want to replace anyways, just might be sooner.

If anyone has dealt with this before, let me know your thoughts. I would suggest changing out the FPR as with the age of these items, in my case 22 years old, the diaphragm will just go bad over time. $100 can pay itself if you save $5 bucks a month on case for the next 10 years.