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Fuel pressure regulator test/repair?

1985 BMW E30 320i ...

The fuel rail is apparently running at too high a pressure (again). The pressure was causing the fuel inlet at the bulkhead end of the fuel rail to leak and spray petrol everywhere. I fixed the leak (moved the jubilee clip a bit, retightened), but then the pressure blew the coupling between the fuel filter and fuel rail apart :-( Fixed that, but the pressure is so high that the engine is running very rich.

My guess is the the fuel pressure regulator on the other end of the fuel rail isn't dumping enough, or any, excess fuel back to the tank. Before I spend 50 quid on a new FPR (doubling the value of the car!), can I test or repair the existing one?

I thought about removing the return hose and seeing if any fuel was actaully coming out of the regulator, but if there is I do know what this will prove.

I can't test the fuel rail pressure (no gauges to hand).

Oh, the fuel pump is very noisy, but I think that's a symptom rather than the cause.

This happened a few years ago, but then magically fixed itself and ran for

2 years without any problems!

Al.

Reply to
Al
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The fuel rails shouldn't leak at the maximum pressure the pump is capable of - not very much above the running pressure.

You can test it by measuring the pressure. You can buy suitable gauges on Ebay - although plumbing them in may be difficult. You could even use a tyre pressure gauge but the same applies. Has that model got a cold start injector? The hose to that can be a good gauge fitting point as it isn't needed when running.

However, the regulator reduces the pressure according to the engine vacuum - no vacuum maximum pressure, maximum vacuum lowest pressure. Are you certain that vacuum connection is clear and in good condition?

If there was no return the pump would stall. And probably burn out.

If the pump is running at higher pressure than the correct one it could well be more noisy.

Reply to
Dave Plowman (News)

Finally got around to looking at the FPR ...

I am now. The vac pipe is clear and fit for purpose. Pity, it would have been an easy fix.

I did remove the return, and blowing through it suggests that it's clear. The engine runs fine without it, but it did dump a lot of petrol into the vessel I put under the FPR outlet.

The FPR seems to be working perfectly from what I've seen today. Oh well, another semi-cheap fix bites the dust ;-)

Having eliminated everything else, it's got to be the pump. Dunno why it's decided to go mental again, and am not looking forward to replacing it :-(

Cheers for the feedback - Very helpful. Next job - Fuel pump replacement; Hints and tips welcomed!

Al.

Reply to
Al

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