m20 325i wont fire

[Matty104 0]

Hey guys ,

Needing some help here,

*so my e30 325i starts fine when its cold, but ( not every single time but more often than not ) when warm it will crank over for a good 10 seconds before it will fire,

*To throw another spanner in the works if i let it crank for say 5 seconts , switch the key off then crank it again it will fire straight away.

*when lowish on gas if i come around a tight corner and accelerate it will cut out for a little bit then carry on its merry way.

I have replaced the fuel pressure regulator with a second hand one but no luck,

so now im stumped

any advice greatly accepted..

Matt

Edited May 4, 2009 by Matty104

[kerrynzl 3]

Sounds like a Fuel pump issue eg: blocked pickup [ when you switch it off for a moment all the crap clears a bit ]

also check the current draw while cranking it [ the starter might be drawing too much for the F/pump etc ]

[Jamez 2147483647]

have you actually checked if your getting the right fuel pressure? when i first got my 325i it had a fuel leek in the engine bay and under hard acceleration it would cut out almost, but now its all sused its fine

my hypothesis is that when its cold the rubbers are less expanded meaning they can hold a greater pressure, with them expanded what ever is pumping the fuel threw, has to pump to a greater area

also turning it off and on causes the fuel relay to do a kinda pre pump were it just pressurizes the fuel line

i found when the fuel injectors were not working on my m20b20 if i turned the key on,off,on,off it would force enough fuel threw so that when the ignition was turned on fully it would run for a few seconds

also i have read a full tank of fuel can give a little bit more fuel pressure to give a tiny bit more performance because the fuel pump doesn't have to work so hard

whole lot of jumble lol hope that gives you some ideas

[Matty104 0]

heres the situation tonight

i have figured out that i need to install a check valve in the fuel line, this question is proving hard to answer,

Where do i mount the check valve?

what does this 'Check Valve" look like?

And does anyone have a part number of the valve i need? 735il check valve?

[Guest FrantiC]

I don't think you are on the right track dude, There is no check valve in the fuel system. Only valve is for the fuel evap canister system thing.

[Matty104 0]

yeah i no theres no check valve in the original system

But every where ive searched has said to chuck one in,

because basicilly the system wont hold the pressure and so the fuel is flowing back down the hose into the tank when warm so the excesive cranking is to suck the fuel back up, a one way valve would stop it flowing back thus leaving the hose full, so fuel is there as soon as you turn the key.

Can't hurt to try as the part seems to only be $10ish

Hope that makes english

[*Glenn* 854]

On an E30 the external high pressure fuel pump has a built in non return valve built into the pump outlet

[Guest FrantiC]

Yeah, if it didn't need one in the first place I don't think adding one will change anything. Could be bad injectors.. leaking and flooding cylinders..

[Matty104 0]

On an E30 the external high pressure fuel pump has a built in non return valve built into the pump outlet

Therfore this could be faulty within the fuel pump?

Would it benifit more to replace the fuel pump?

heres one of the links i can remember off hand there was quite a few others relating to adding one into a e30 m20

Link

Edit Part Number 16149068988

and LINK which is EXACTLY what i needed to know, except mine has and external pump so will be fitting in just after the pump

Edited June 11, 2009 by Matty104

[bimmer boy 21]

When I researched the problem I too always came up with that valve. A fuel pump might be beneficial but I dont think it will solve your problem as a faulty fuel pump surely wouldnt cause a car to have trouble only during a hot start would it? Who knows, its an annoying little fault aint it!?

[Matty104 0]

sure is annoying, the kits only $7 so cant hurt to try

[*Glenn* 854]

Have you actually put a fuel pressure guage on it to see if you are loosing pressure and the fuel is draning back into the tank ?

[jochen 4]

Hey guys ,

Needing some help here,

*so my e30 325i starts fine when its cold, but ( not every single time but more often than not ) when warm it will crank over for a good 10 seconds before it will fire,

had a car with the same symptoms once

Was a cracked cylinder head - would hold compression pressure when cold, but not when hot.

Measure the compressions

[320guy 0]

Sounds like fuel pump to me. The little non return valve in the pump probally has crap in it jamming it open, and if its got crap in it, its probally stuffed.

While your cranking the engine give the fuel pump a good whack / whack the tank. Even if it isnt holding pressure when you turn it off a good pump shouldnt take more than a second or so to re prime the lines and pressurise them.

Your car should have the single intank pump.

My car had similar symptoms for a long time, until it wouldnt start at all most the times without giving the tank a whack, then a few weeks later it died completely.

You shouldnt need an additonal check valve, they work fine from the factory with out one, putting one in would just be a bandaid. But if you were to put one in, put it at close to the tank / fuel pump outlet as you can.

Edited June 11, 2009 by 320guy

[hotwire 352]

As Glenn has said - check / have checked the fuel pressure/flow. This will confirm pump/lines/pressure regulator are all ok

If starting OK from cold then unlikely to be fuel draining back. If it was then - a delay may be expected.

Fuel delivery is atleast 2.5 litres per min at about 33psi so lines/rail refill quickly anyway.

Being that the problem is when warm & if it is infact a fuel problem & pump OK then more likely leaking injectors