Hard Starting - 1990 535i

[hdaemon]

So for the last week or so, my '90 535i has been having difficulty starting. More than half the time, when I turn the key, the engine will crank, but it doesn't sound like it's even trying to start (no sputtering/etc). If I stop turning it over and try again, it start almost immediately. If it does that the first time, it ALWAYS starts on the second try, almost immediately.

The problem started abouta week ago, after a weekend road trip I was taking. I can't remember if it started on the way back, or after getting home. The only thing that's been changed in the car in that time is the gas.

Any ideas where to start looking?

[George M]

maybe a fuel line bleed down issue due to an ailing internal check valve in the fuel pump. May also be something obtuse like your ignition switch if not your main or fuel pump relay making better contact the second time. Try the following. Turn your ignition key to on but do not turn the key immediately engaging the starter. See if your fuel pump will fill the line prior to cranking the engine. Then turn the key the rest of the way and see if it fires on the first attempt. Consider performing a fuel pressure check at some point as your pump may be dying.
HTH,
George

[hdaemon]

maybe a fuel line bleed down issue due to an ailing internal check valve in the fuel pump. May also be something obtuse like your ignition switch if not your main or fuel pump relay making better contact the second time. Try the following. Turn your ignition key to on but do not turn the key immediately engaging the starter. See if your fuel pump will fill the line prior to cranking the engine. Then turn the key the rest of the way and see if it fires on the first attempt. Consider performing a fuel pressure check at some point as your pump may be dying.


So after a few days of experimentation, it seems as though this is the likely culprit. Letting the car sit with the ignition on for 20-30 seconds seems to ensure that it will start up on the first try.

That leads to a new question:

Is a fuel pressure test something that can feasibly be done by someone with a reasonable amount of repair knowledge and general mechanical aptitude? What special tools are required, and how much would it cost me to obtain them? (ie - is it worth it to try doing myself or should I just have my local shop do it?)

If the fuel pump is dying, I'd prefer to replace it myself and save myself the labor charges of having someone else do it. Although I do need to first figure out which fuel pump is in there.

[winfred]

id be thinking along the lines of a bad electrical connection, fuseable link, relay, the little power connection inside of the box on the right side with the brain.....

[hdaemon]

id be thinking along the lines of a bad electrical connection, fuseable link, relay, the little power connection inside of the box on the right side with the brain.....

I'll definitely be sure to check there. Is the specific location easily describable? My Bentley is current AWOL and the new copy hasn't yet arrived.

And that still leaves the question of how easily a fuel pressure test is performed. My fuel pump has been making noise for quite a while (more noticeably recently) so I wouldn't be surprised to find it to be the culprit.

[Javier]

First you should insert a gas pressure gauge in the gas delivery hose, best to do is to get a "T" tubing and some gas hoses. For the M30, there is two gas hoses running up at the drivers side of the engine, the rear most is the incoming fuel line, lets call it "MAIN HOSE", it attaches to an "ALUMINUM TUBE" that goes up behind the intake body, and bends 90 degrees to the back of the car ending in a small hose (about 1 ½"-2") that connects to the rear end of the injector rail. You can detach the Main hose, connect to the "T", then complete the fuel line connecting a small hose between the T and the aluminum tube, and the connect a second hose between the "T" tap and the gas gauge (0-100 psi, expect a reading of about 43 psi).

Remove the second hose (returning hose) besides the Main hose and attach a new hose to the aluminum tubing, provide a suitable container to collect returning gas. Tapping the bottle here will not confirm the returning hose up to the sender, below the carpet in the trunk, is OK (free of obstructions), but is easier than going back to the trunk, identify the returning hose and put there the container, also returning hose should not be a problem.

1.- Bypass the fuel pump relay with a jumper for 30 seconds (accurately time them), the pump should flow 29.6 Oz of fuel to the container, the pressure gauge should read 43 psi for the M30.

2.- Once the pump is stopped, the pressure should holds above 38 psi for at least 20 minutes.

Low fuel flow may indicate faulty pump or clogged filter. If the flow is OK but the pressure is low or does not hold, clamp the returning hose to the container and run the pump for a couple seconds. If the pressure rises OK and holds, then the fuel pressure regulator is faulty, if the pressure keeps low or does not hold, then you have a leak in the system, either an injector, a hose or the check valve at the pump.

I can not tell you prices, may be somebody else can help you there.

I would say you are loosing pressure in the system (leaking somewhere). 535i typically leaks at the small hose connecting to the back of the injector rail.

[Jeff N.]

Simple check. Bentley's has the final detail but from recollection your CPS must be about 1mm from the harmonic dampener.

If the distance is more than the spec, the car is hard to start.

Jeff