True or False

[chefmike70]

If the air boot has a hole in it the car will not run. True or False?

I have been messing with my 87 325 for 3 months now and still can't find a solution
Car cranks and starts. Will run for 5-20 minutes then the motor cuts off. If I let it sit for awhile it will crank and start to fire but will not catch.
I have replaced:
fuel filter
main relay
fuel pump relay
cps
fusible link

I have checked:
ground cable and connections
spark
fuel pressure at bar
various other items I have found by searching similar posts

I found a small gash in the bottom of the air boot today. Can this keep the car from running?

What else can I check?

[jlevie]

If the air boot has a hole in it the car will not run. True or False?

Both true and false, depending on the size of the leak. With a small leak the engine will run, but idle and low rpm operation won't be right. With a big leak the engine may not even start.

This could be a closed loop operation issue. On a cold start the DME is running in open loop mode and only using data from the AFM, IAT & ECT sensors, and rpm. Once the engine is hot enough it adds data from the O2 sensor to fuel & ignition computations.

Or it could be a temperature related fault. When you did the fuel pressure check was the gauge in place for the successful start, the dying of the engine, and the re-start attempt? Likewise for the spark check?

[chefmike70]

The air boot is split about 3" on the bottom. It must have split when replacing the air filter. I have ordered a new one.

I only had the fuel pressure gauge briefly to check that there was adequate pressure.

[dnguyen1963]

Buy some shoe goo and seal that crack for now.

[jlevie]

The air boot is split about 3" on the bottom. It must have split when replacing the air filter. I have ordered a new one.

I only had the fuel pressure gauge briefly to check that there was adequate pressure.

You can make a fuel pressure gauge pretty cheaply. A 60psi gauge like used on water systems can be had from Lowes, Home Depot, etc. Some 5/6" barb fittings (connection the gauge and a barb tee) and some FI hose and clamps finishes it off. 5/16" barb fittings can sometimes be found at a plumbing supply or auto pars house or always at MSC or McMaster-Carr.

You really need to know what the rail pressure is the a start/die/re-start failure.

[chefmike70]

So I have a fuel pressure gauge tee'd into the system. When the car starts its about 28 psi and stays there. When the car dies its at close to 40 psi and stays there. Some time later it will drop to below 30 and the car starts. So is this the fuel pressure regulator?
Also when it is running the idle is fairly high-can't say exactly what it is as tach doesn't work- but it is noticibly higher than normal.

I have replaced:
all vaccuum lines and checked the connections (local shop doesn't want to work on a BMW so I haven't done a smoke test)
the cps
main and fuel relays
the main air boot

[jlevie]

An 87 325 would have an ETA engine, fuel pressure at idle would be about 30psi at idle and 36.7psi at WOT. If the car is an 87 325i/is/ic idle should be about 38 psi and 44psi at WOT.

The high idle and other problems suggest the presence of intake leaks. You really need to find a shop that can run a smoke test.

[andrewm]

So I have a fuel pressure gauge tee'd into the system. When the car starts its about 28 psi and stays there. When the car dies its at close to 40 psi and stays there. Some time later it will drop to below 30 and the car starts. So is this the fuel pressure regulator?
Also when it is running the idle is fairly high-can't say exactly what it is as tach doesn't work- but it is noticibly higher than normal.

Sounds like fuel is backing up, so maybe a clogged return or busted FPR. It COULD cause your trouble, but that doesnt seem high enough to me. Based off knowledge when Ive had FPR issues on other vehicles, might be the e30 is more sensative to fuel pressure though

[chefmike70]

My car is a 1987 325 (no letter after the number) built in 02/87
When I start the car it fires up and runs for a few minutes the gauge shows 28 psi. I can sit and watch the gauge for a few minutes and it pops up to 40 psi and the motor shuts off and I NEVER touched the throttle. If I let it sit for awhile the pressure drops off and I can start it again-without touching the throttle.
I figured if I can get the motor to run long enough I can get it to a shop in Tyler that will work on the high idle.

[chefmike70]

also, if I immediately disconnect the fuel line from the rail, let the pressure drop off, reconnect the line and crank it-without touching the throttle- the pressure goes back up to 40 psi and it won't start.