M10 Engine Issues

[Baurosarus]

Hi all,

Thanks for all your time in advance. Admittedly I don’t have an E21, I’ve a 1986 318i E30 Baur, but thought this might be the best place for any obscure m10 engine queries!

Car is completely standard engine wise. It’s recently has a minor restoration and has new fuel pump, new distributor cap/ht leads.

I experienced it starting to die whilst driving the other day, but was simply a case of turning the ignition and it firing to life again. Unfortunately this got to the stage were it didn’t start at all and I had to recover it.

I’ve had it a few weeks now. It was driving ok enough upon receiving it. It stuttered a bit under gentle load, but all it needed was a healthy dose of throttle to run smoothly.

I’ve tried some troubleshooting. The car has spark. There doesn’t appear to be any vac leaks. I removed the fuel pump fuse (11), depressurised the system and confirmed that the fuel pump is providing fuel to the rail ok.

Strangely with the fuel pump fuse removed the engine actually runs, albeit it a bit lumpy. I presume the system isn’t working when pressurised with fuel, but works fine when not pressurised? Could this be an issue with the valve on fuel rail?

Thanks for reading all that, grateful for any pointers!

Rick
(Based in Belfast)

[Wilmo]

My first guess would be to verify the timing. Second to check whether all injectors fire or that one maybe lags.

[Baurosarus]

Cheers, will be trying both in the next few days here. Fingers crossed…

[BertjeConti]

If i'm right your 318i is a LJet fuel injection.
If your engine runs and keeps running without the fuelpump running, you have a very special car.
No, a ljet can't run without pressurised fuel present in the fuelrail.
I gues your fuelpump relay is faulty, and fails at the moment the engine stalls. Fuelpump relays are a common known issue.

[Jeroen]

On the other hand, with no power to the pump, usually the engine will still be running for a while on the residual fuel in the system. It could definitely be that the fuel pressure regulator is at fault, could be an internal issue or a bad vacuum to the regulator. In most cases, the fuel pressure is probably too high, explaining why it may be running better, at least for a few secs, with the fuel pump disconnected electronically, as that results in a lower fuel pressure. To be sure, you could test fuel pressure or do an exhaust gas analysis. After you make sure ignition timing is spot on both static (without vacuum advance/retard) and dynamic. The latter could be messed up with a bad vacuum connection.

Any changes to the engine setup around the time the issue started?

[Baurosarus]

Hi all, appreciate your help with this. Re running without the fuel pump, it was only on residual fuel in the system and lasted 15/30 seconds! I think I’ve worked out the issue. I fettled with the idle control earlier and it now seems to be running fine, starting on the button. Watch this space…