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Poor starting / flooding

gordonjcp

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#1

Over the past wee while my V8 has developed an odd problem where if it's been switched off for a while it is very hard to start and will eventually splutter into life missing like hell with a big puff of oily petrolly-smelling exhaust fumes. It's like it's severely flooded. Starting on petrol only makes no odds.

If I pull the fuel pump relay I get the usual takes-ages-but-starts-on-gas thing. I ran around with no fuel pump for a bit and while needing it to crank for ten seconds was a bit of a pain in the arse it worked okay. After I replaced the fuel pump it started okay on petrol but started this flooding crap.

Any thoughts?

Morat

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#2

Leaky injectors? Can you do a leak down test on the fuel rail pressure?

gordonjcp

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#3

I wondered about that. There seems to be plenty pressure on the fuel rail but I don't have a way to measure it.

Gilbertd

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#4

Haven't you got a tyre pump with a gauge? As long as you blast air through it afterwards to get the petrol out of the hose, it should be OK.

gordonjcp

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#5

Ah, that would work, yes. In fact I think I've got one of the slidey metal tube tyre pressure gauges...

Gilbertd

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#6

Check it when you've first turned the engine off and again after it's been standing. If the pressure has dropped then it's either leaking back through the regulator or through the injectors.

Morat

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(Last modified: by Morat)
#7

You can check if it's the regulator by turning the key to 2 for a couple of seconds 2-3 times before cranking. It'll trigger the fuel pump and should pump the rail full again. Well it does on any other vehicle I've owned. A P38 might have some special BECM control function that takes into account tide state and Moon phase.
If it's the regulator the engine should then fire right up and of course, if it's the injectors it'll flood even worse!

One of these should do the trick Much Cheapness
Does anyone know the spec for fuel pressure? Google says 3.5 Bar but I don't have Rave here.

Hook it up, and watch the pressure at cold - idle - off then see how it leaks down over 15 minutes. On a Jeep you'd be looking for 49 Psi +/- 5 Psi

Gilbertd

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#8

GEMS is 34-37 psi

no10chris

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#9

Exactly the same as mine, I’m pretty sure mine is O2 sensor related, Do a live scan see what there doing,, mine is definitely over fueling

no10chris

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(Last modified: by no10chris)
#10

Found one of the pins on lambda had pushed back, reseated and I’m running much better, let’s see if it cures my starting problems,,
So definitely check your lambdas

Aragorn

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#11

Try unplugging the MAF. It'll take two or three goes to start it without the MAF plugged in, but it should run fine once it starts.

I had an issue with mine doing the "belching black smoke and missfiring" and it was a bad MAF that was to blame.

Morat

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#12

Gordon, have you scanned the Motronic for faults yet?

Gilbertd

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#13

Morat wrote:

Gordon, have you scanned the Motronic for faults yet

Difficult as it's a GEMS....... Although checking for any fault codes is always a good place to start.

gordonjcp

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#14

There aren't any faults stored, but the driver's side lambda seems to have less "range" than the passenger side - it doesn't appear to go all the way down to 0 or all the way up to 5, but it does switch more or less in time with the passenger side one when it's on gas.

I wouldn't have thought the lambdas would make a huge difference at startup since they're stone cold! One thing I have noticed is that on petrol the fuel trims whang up to +25% at anything above the slightest touch of throttle, so I wonder what's upsetting the whole thing?

Gilbertd

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#15

If the MAF is giving a high reading, then it will dump more fuel in to keep the mixture correct. But I wouldn't have expected that to affect starting.

Morat

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#16

Have either of the O2 sensors been replaced in your ownership? I'm wondering if they're both the same spec. But.. as said - they shouldn't affect anything at startup while the engine is still on open loop. In fact, I'm trying to think of anything that would affect fuel trims in open loop - or are you only seeing that behaviour once the engine has warmed up a bit?

Gilbertd

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#17

Mine is encouraging me to walk to the village shop to get my fags. If I start it from stone cold, run the 400 yards or so to the shop (on gas or petrol, makes no difference) and then turn it off, it's reluctant to start unless I switch it to start on gas and give it a big bootfull of throttle which would suggest it has a bit more fuel there than it needs. If it has warmed up a bit more, it starts on the first turn as it always does any other time.

The other time I've had starting problems is if the evap valve decides to open and flood the inlet manifold with petrol vapour. Then it will start but run really roughly, if I keep it running for 30 seconds or so it clears or I can switch it off, restart and then it is fine

Lpgc

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#18

Could just plug the evap line Gilbert, maybe save a bit of petrol too.

Gilbertd

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#19

I would if it was doing it regularly but it's just the very odd occasion, like once every 6-9 months, so not worth messing around. Saving petrol isn't that high on the priorities, I've still got the same petrol in the tank I put in about 5 months ago. Currently running on LPG at €0.45 a litre, that's under 40p.....

Lpgc

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#20

Yeh that makes sense Gilbert

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