e30 starting issue (fuel pressure?)

[dubman 39]

The car didn't start 3 weeks ago, and now it has occured twice more. After pulling the fuel hose before the fuel rail (I didn't jump the relay for fuel flow test), the car started nicely with the fuel hose disconnected. After the 2nd time it didn't start, I did the same thing but with no luck, and after changing the fuel filter....it started.

2 days ago, car didn't start again. I put in a new pump today just in case (I know it's bad to throw parts into a unproperly diagnosed issue) as after some reading, the only two things that came up were fuel pump issues, or the fuel pressure regulator was shot (fuel pump was the cheaper of the 2, and mine was old)

Check list:

Spark: good

Fuel pump and relay: good (new pump put in 30th Nov)

Temp sensor, engine pulse/crank sensor: good

Vacuum lines and intake gaskets: good

Since pulling fuel lines made the car start, I'm now thinking its the fuel pressure regulator causing the issue, or a blockage in the fuel return line. The fuel return line right before the fuel pump had very poor flow rate (around 1/3 or 1/4 of the pump flow).

The car ran briefly when I cranked it with now fuel pump. The common factor with all 3 starts after a "no-start" was the absence of pumped fuel.

Would love to hear anymore feedback on my gremlin chase (getting pretty ticked off about it). It's either on a tow truck off to Glenns or stumbling there haha

edit: updated progress with the BS cut out, coz now i'm just annoyed at it

Edited November 30, 2013 by dubman

[Paragon 14]

Recently I had a slower than normal start up, occasionally at times a low load miss, every now and then no start. Then the idle l got erratic and it kept blowing fuses so I had no tacho.

After a lot of chasing around it developed into a intermittent miss under load. The next day it was okay and it got a thrashing that day. Following morning it wouldn't start, not at all.

Turned out to be a crank sensor.

[_ethrty-Andy_ 2132]

Recently I had a slower than normal start up, occasionally at times a low load miss, every now and then no start. Then the idle l got erratic and it kept blowing fuses so I had no tacho.

After a lot of chasing around it developed into a intermittent miss under load. The next day it was okay and it got a thrashing that day. Following morning it wouldn't start, not at all.

Turned out to be a crank sensor.

seems strange, typically the crank sensors seem to just die or work, maybe the intermittence comes from a dodgy connection?

also worth checking fuel pump relay, thats more likely to have an intermittent issue.

[dubman 39]

cheers for sharing the advice guys!

Car didn't start again today, and no dice after following the procedure in the 1st post......regardless of the cause, I pulled apart the intake manifold to have better access to the crank sensor connectors, whilst changing intake manifold gaskets + fuel hoses just for maintenance sake. Will see how it goes.

[_ethrty-Andy_ 2132]

Is this car running a BMW or Link DME?

if you want to check your CPS, instead of getting down inside the engine, check it at the DME, you need to check the resistance on the loom side between pins, i think its pin 48 and 49 from memory, or look at a ETM for your car. If it even is that.

[dubman 39]

running BMW

I might as well check the sensors at the connections etc and make sure everything's in good shape. When I pulled the intake manifold, someone used gasket glue with the paper gasket. I ended up scrapping for 20 mins to gently clean the old gasket off, and there was alot of crud surrounding the intake port. The old fuel rail hoses were also cracked (got lazy and didn't do them when engine was out of car).

Its an intermittent issue, so i'll read more material etc. to see if anything comes up, and do some maintenance whilst at it. At least i know it won't run now, better than be let down unexpectedly.

i also got a spare fuel pressure regulator, will chuck that in to see if it starts again (hopefully the spare's not f*cked haha)

Edited November 20, 2013 by dubman

[dubman 39]

SO.....chucked in my spare FPR, cleaned all terminals underneath intake manifold, and did some gasket/hose changes and the car still didn't start!

After, I checked fuel flow pre-filter and re-connected my fuel filter, then gave it another shot. IT STARTED!

By now, the sun had gone down and my cabin temperature has also gone down. When the car failed to start both times, it was at around 4.30pm, when the car had a full days sun exposure, and running on a near empty tank.

The words "Fuel Check Valve" keeps popping up whenever I read about similar non-start situations. If it fails again, probably get it to Glenns for legit diagnosis.....but for now I'm thinking it's fuel pressure related and I don't have the proper tools to diagnosis it correctly.

I don't want to aimlessly throw new parts at it, better to fix it right 1st time around

[_ethrty-Andy_ 2132]

At least i know it won't run now, better than be let down unexpectedly.

very true, lived like that for ages in my first e30

[dubman 39]

and back to square 1....didn't start.

Will being picking up a new pump from Gavin tomorrow, and off to Glenn's for a checkup next week regardless.

Body's done 250,000kms already, and pump looks that old

Edited November 30, 2013 by dubman

[dubman 39]

New pump put in, and still no dice. It did run with no fuel pump so still looking at fuel pressure issues.

Either something's causing a restriction on the system (blockage) or the fuel pressure regulator's dead. Fuel return rate pre-pump is very low, and pre-fuel rail is very good.

Edited November 30, 2013 by dubman

[Etwenty1 45]

Check valve is non return valve to hold pressure after shutoff. Might allow car to run briefly with no pump but sounds odd. Have you tried jumping the fp relay to get car running?

[dubman 39]

hey Chris, no, because when the car started up both times without pumped fuel, I had a 1litre bottle to catch the fuel from the fuel filter, and the fuel rate was good. Also, it's been daily driven etc. between "no start's" so I thought relay would be o.k.

Today, the car started again, with fuel hose pulled, and ran well after putting the hose back in again.

I did pull the vacuum hose off the FPR the day before every time the car died to see if the diaphram leaked....I just remembered that today, so maybe that caused fueling issues?

[dubman 39]

update on this. Took the car to Glenn's, and the FPR is working (2.5 bar w/vac, 3.0 w/out vac), ICV's good (although one of the piping's a bit constricted, will be changed), and TPS is working.

However, manifold vacuum was slow to build on startup, and fuel pressure was raised to 3 bar for a moment. This in combination with my side-lain AFM, long intake piping, and rich fuel mixture, lead to difficult starting.

Thanks again to Glenn @ Botany Motorworx for providing me with quality advice and diagnostics. chur chur