350i starting issue

350i starting issue

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Pumpkin123

Original Poster:

16 posts

11 months

Thursday 16th May
quotequote all
Don't know if anyone could offer any advice but having trouble starting the beast. So the other day decided to go for a spin, car started as per normal drove out of garage onto drive, got out to shut garage door and the cars idle slowly reduced and conked out. So went to restart and car totally dead, turns over ok but does not fire.
So seem to get pretty good spark, plugs seemed wetttish.
Checked the resistance of various sensors, ie coolant temp, thermotine, and all seemed ok.
Checked for air leaks, replaced a couple of hoses which looked slightly perished but all seemed ok.
If I put igniton on and blip throttle, injectors all click.
Fuel pump runs if I operate the AFM vane.
I have a foxguard alarm which looks like its disabled, although not entirely sure.

So at this point I gave up and decided to buy a pressure gauge to check fuel pressure. So having left the car for a week, I thought turn the key and see what happens and car fired up first time, drove car out onto drive left it running for a bit, got out to shut garage door and it conked out never to restart again.....sigh!

There does appear to be some sign of life now, like it thinks about starting but doesn't.

So checked fuel pressure and I'm guessing there's something not quite right here but can't believe this isn't why it doesn't fire up. So attached gauge to 9th injector, (have to say didn't purge air out of the line) and when you run fuel pump it reaches a max 45psi, but when you turn off fuel pump it immediately drops to about 38psi and then over the course of a minute drops to about 25psi. If I start to pinch the fuel line back to tank, I can get more than 45psi.

So I'm at a bit of a loss, I'm a bit conscious that I don't want to go tearing too much apart and causing other issues, but just wondered whether anybody had any ideas as I'm wondering whether I'm missing the obvious here.
Any help obviously greatly appreciated as I'm suffering with wedge withdrawal symptoms.

dimitrivdw

21 posts

43 months

Thursday 16th May
quotequote all
You tried starting while pushing the throttle? I'm thinking about that when you say the plugs are wet.

That's a possible way to get her started again, but not sure that will fix your issues smile

mrzigazaga

18,265 posts

106 months

Thursday 16th May
quotequote all
Hi

It sounds fuel related.. if you have the original fuel pressure regulator on there still then the diaphragm inside could be perishing, normally if cars are sat around for long periods of time the rubber dries out and starts to crack.

The solid state regs as per original should be set to 36psi...for a 350i...its nothing or all with these and this is why people fit adjustable rising regs...if you have a adjustable reg on there already then it sound like the fuel pump is failing, especially if its only pumping 45psi with the return clamped, should be more like 65-75psi....

Hope this helps


Ziga smile

adam quantrill

10,734 posts

183 months

Thursday 16th May
quotequote all
I would say with those pressure readings there is enough fuel pressure to run the engine.

Next time do not get out to close the garage door!

Sit in the car and raise the idle to 1500-2000 with the throttle. Note what is happening (get someone to observe).

Let the engine temp rise up to at least mid way, still do not get out of the car, let the engine return to idle. If it sounds like dying, open the throttle.

Look out for black sooty stuff out of the exhaust, and report back with any other observations.


Pumpkin123

Original Poster:

16 posts

11 months

Hi, thanks for the replies.
In answer to questions:
1. No giving throttle doesn’t help starting.
2. On the regulator front, I hadn’t realised there were different ones, i’ll have to do some investigation there once I get it running again. As for fuel pressure I get loads, I ran up fuel pump and started to pinch fuel hose returning to tank and it went up to 60psi. It probably would have gone further but I started to get worried about whether I’d done the jubilee clip on the pressure gauge up properly and didn’t want the fire it into oblivion. But thanks for the info on pressure regs.
3.adam, yes the car started on those 2 occasions and looking back I’m slightly annoyed that I let it conk out but at the moment I can’t get it started at all.

I’ll have another look Saturday, having done lots of reading can’t help but think it’s a fuel issue as mark said. I’m thinking next step is to attack the aux air valve at the front and measure sensors from the ecu connector. I’ll keep you posted, any bright ideas and please let me know as I’d prefer to be out driving it than fixing it.
Cheers Pete
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Pumpkin123

Original Poster:

16 posts

11 months

Hi, thought I’d just add some closure to this one but after a lot of sodding around I finally discovered that my throttle potentiometer had been adjusted right to the end stop, so I was getting 0v as opposed to the 325mv as expected. I’ve never adjusted this so I don’t know what that’s all about, but I’m guessing the cars going to fail on emissions at the next mot. Does anyone know if there’s a reason why you’d adjust this potentiometer like this?

On the plus side car now goes like a beast and starts instantly as opposed to the 4 second delay before. I’m slightly confused as they say in the manuals that the throttle pot makes little difference to ecu and that people often disconnect them.

Need to sort out the slight fuel pressure seepage now, my fuel pressure reg looks old so might replace anyway. Any suggestions for pressure regs, are the rising rate the ones to go for?

I noticed in the manual it says if you fit a rising rate reg you need to adjust the extra air valve at the back of the plenum.

Anyway off to drown out the ford tuner boys that seem to have invaded the place this weekend.

mrzigazaga

18,265 posts

106 months

Hi mate


I have a Sytec adjustable fuel reg on and it has a glycerine filled pressure gauge which can be left on, if you use the Malpassi or FSE rising rate regs then you must connect up a gauge only when initially setting up...I prefer the type that you can leave on as it helps to diagnose stuff sometimes...not heard of having to adjust the over-run valve...although mine was closed to create more pops and bangs..smile

Not sure that any would run without a TPS...how otherwise would the ECU know how much fuel to give if its not being called for by the throttle?...

Hope this helps

Ziga smile

adam quantrill

10,734 posts

183 months

Yesterday (09:45)
quotequote all
I had a wiring fault where the TPS wires had an intermittent short to ground, that did kill the engine, then it came back to life, then died. Took a while to find that one. So the TPS is a necessity.

Pumpkin123

Original Poster:

16 posts

11 months

Yesterday (16:26)
quotequote all

Thanks for the info on fuel regs, I'll get one on order in a mo,

Ha, yes intermittent faults are always the best, as I've come to realise 325mV makes all the difference.