residual pressure gremlins

[nariusb]

I'm ran out of options to fix the loss of my residual pressure. It leaks out in two hours or less.
I tried all the options with the help from search. Here's what I'm done:
- Installed the check valve fix kit in the trunk, just above the fuel pump,
- replaced rubber fuel lines and clamps,
- recent fuel filter replacement,
- no gas smell,
- replaced fuel injectors with O-five ones (delco),
- clamped fuel return and then fuel supply lines (it still leaked, so I guess FPR is OK)
Where in the ... does it go??? The search shows similar problems but stops short of fixing the problem. Let's get it this time for future e34 guys.

[nariusb]

I'm ran out of options to fix the loss of my residual pressure. It leaks out in two hours or less.
I tried all the options with the help from search. Here's what I'm done:
- Installed the check valve fix kit in the trunk, just above the fuel pump,
- replaced rubber fuel lines and clamps,
- recent fuel filter replacement,
- no gas smell,
- replaced fuel injectors with O-five ones (delco),
- clamped fuel return and then fuel supply lines (it still leaked, so I guess FPR is OK)
Where in the ... does it go??? The search shows similar problems but stops short of fixing the problem. Let's get it this time for future e34 guys.

Just to mention it's 1989 525i with m20 engine. The car runs great. The only little problem I have is a little longer, about 2 or 3 seconds, crank time.

[Kalevera]

What does the metal send line look like? I think you've tracked down the problem. Clamping the send and a correctly installed check valve (don't think it can be mis-installed and have the car still run) isolates the send line. I'd go over the whole thing with my sniffer...it's gotta be leaking somewhere.

best, whit

[nariusb]

What does the metal send line look like? I think you've tracked down the problem. Clamping the send and a correctly installed check valve (don't think it can be mis-installed and have the car still run) isolates the send line. I'd go over the whole thing with my sniffer...it's gotta be leaking somewhere.

best, whit

Thanks Lowell,
The lines looks solid and I don't smell any gas but since it's a very small leak you're could be right on the button. What' s a sniffer?

[Kalevera]

Your nose

There are differences between what a full fledged LEAK will smell like versus a vent leak (ie -- a hole on the top of the tank). Given that the pressure is bleeding off so quickly, I'm betting the line is bad at some point. No other way to go about it beyond getting on a creeper and sliding around under the car/inspecting every inch of that line.

Edit: argh, now that I think about this more...I'd be suspecting the line IF the engine is running normally (ie -- no indication that the FPR isn't doing its job) and the fuel rail itself isn't leaking. There're a few intake related susceptibilities on the M20 that will make things run poorly. I'm assuming that you've got an in line fuel pressure gauge that you're basing a hard start issue on...

best, whit

[nariusb]

Your nose

There are differences between what a full fledged LEAK will smell like versus a vent leak (ie -- a hole on the top of the tank). Given that the pressure is bleeding off so quickly, I'm betting the line is bad at some point. No other way to go about it beyond getting on a creeper and sliding around under the car/inspecting every inch of that line.

Edit: argh, now that I think about this more...I'd be suspecting the line IF the engine is running normally (ie -- no indication that the FPR isn't doing its job) and the fuel rail itself isn't leaking. There're a few intake related susceptibilities on the M20 that will make things run poorly. I'm assuming that you've got an in line fuel pressure gauge that you're basing a hard start issue on...
best, whit

You say:There're a few intake related susceptibilities on the M20 that will make things run poorly
What are these susceptibilities?
And yes I have an fuel gauge on the suply hose.
I just inspected the lines again very carefully and I don't see any week spots or smell anything. Can a pin hole in the tank above fuel level cause it?

[632 Regal]

what does the guage read at idle and when you hit the throttle? Also have you tried turning the key to the on position for a few seconds before cranking it?

[nariusb]

what does the guage read at idle and when you hit the throttle? Also have you tried turning the key to the on position for a few seconds before cranking it?

Reagal, how are you tonight?
At idle it reads 40PSI and when throttle hit jumps to 46-48 and right back when when released throttle.
My key turned to 2 posstion doesn't start the pump. Should it do that in 11/88 made 525i with m20?

[wingman]

One of susceptibilities is a fault somewhere in the vacuum system. A cracked 'T'-joint on the manifold side of the brake booster will allow pressure out of the system and cause an uneven idle. Where are you(climate)? I couldn't see from your profile.

[nariusb]

One of susceptibilities is a fault somewhere in the vacuum system. A cracked 'T'-joint on the manifold side of the brake booster will allow pressure out of the system and cause an uneven idle. Where are you(climate)? I couldn't see from your profile.

I'm in Canada. My idle is OK, maybee a rittle louder rumble when in drive, but not a problem at all. It idles at 800 or so. I did the unlit propane/ brake fluid spray on the vacum hoses but could't catch any.
One question. Where's the original check valve at the fuel pump, on the suply or return? Could it be that check valve inside the pump? I installed the external one on supply.