Car won't start... - solved

[chazsandiego]

Hello all, I've had a this 90 535i (190k on the clock) for a few months now and have been making steady progress getting it fixed back up.

The car runs very well but has issues starting. 90% of the time the car will not fire up unless you a depressing the gas pedal. Once it's started the car will usually die unless it is manually held at idle. This does go away after a few seconds of driving. It had been dying more frequently but I have since replaced the fuel pump, fuel filter, fuel pressure regulator, vacuum lines, alternator, starter, battery and spark plugs. I have also confirmed that the IACV and throttle position sensor are functional.

I suspect that it is a fuel pressure issue. I can smell fuel when the car is running but I haven't had any luck finding a leak. Is there a place that is prone to leakage or should I just sit under the car with it running and watch for drips? Lastly a mechanic friend heard me trying to start it up and seemed convinced it was a timing belt/chain issue. However, he did not do an inspection so I have to take it with a grain of salt.

Any suggestions or input would be greatly appreciated as always!

[General984]

Maybe fuel pump in tank?

[zubbie]

Have you checked the CPS? Rotor and dizzy cap? Leaky injectors?

[demetk]

Check that the TPS (throttle position sensor) is providing an idle signal otherwise the ICV (idle control valve) may not be opening up at start thus the reason you need to manually give it more air with the gas pedal.

[chazsandiego]

Have you checked the CPS? Rotor and dizzy cap? Leaky injectors?

Forgot to mention that the crank position sensor has also been replaced. But I haven't touched the distributor, rotor. Is there a way to test or should I just replace? And if my injectors are leaking are there o-rings I can replace?

Thanks for the assistance!

[zubbie]

By pulling the dizzy cap you will see if the contacts are worn an burnt. Unless they look good I'd replace cap and rotor. Leaking injectors are a little harder to diagnose but your symptoms are similar. https://www.injectorrx.com/fuel-inje...uel-injectors/

O rings can be replaced but I don't think that would cause starting issues.

[chazsandiego]

By pulling the dizzy cap you will see if the contacts are worn an burnt. Unless they look good I'd replace cap and rotor. Leaking injectors are a little harder to diagnose but your symptoms are similar. https://www.injectorrx.com/fuel-inje...uel-injectors/

O rings can be replaced but I don't think that would cause starting issues.

Thanks! That link was very helpful.

I feel like a forensic detective sometimes when I'm working on these cars because sometimes you can find clues from previous owners about repairs they may have attempted. I'm mentioning this because the plastic cover for both the distributor cap and fuel rail are missing from the engine bay. Make of it what you will.

Obviously for the injectors new is better than used but I still may check out the junkyard depending on the range of models I can swap injectors with. The cap and rotor I can swap off my e32 for testing purposes. After re-reading that link though my bet is on leaking injectors.

I appreciate the assistance as always!

[zubbie]

You can have injectors cleaned. Depending on where you live there my be a local company that checks and cleans them. Another option is to upgrade to Ford modular injectors.

Design 3 mustang 5.0 19 lbs ones work but make sure to use the M30 OEM O rings. You used to be able to find them on Ebay cheap. Somewhere on this forum is more info.

[moroza]

Fuel pressure is unaffected by throttle position. I doubt that ignition system problems are related, either. I'd look for vacuum leaks (smoke test is best). As for the IACV and TPS - you've determined they're functional, but what about correct resistance across their terminals?

[chazsandiego]

Solved!

At some point the previous owner had replaced the idle air control valve hose and installed the new hose backwards causing the hose to kink up badly. Correcting this mistake has completely solved the issue.



I greatly appreciate the assistance! Also good to know I can use those mustang injectors in the future.

[zubbie]

Always nice to see a solution. Thanks for posting.

Never fails to surprise me how dumb (or lazy) some people are with car maintenance. I bought a truck once that had the front grill and lights held in with silicone sealant. Like he lost all the hardware and thought this was reasonable solution.....