Vapor Lock? - My Issue is Vapor Lock? Causes? Test?

[DaveSmed]

What about your cold start injector valve?
That could be your problem leading to over fueling at warm startup (smell of fuel).
Try leaving it unpluged next time you start your warm engine.
I get your exact problem too, and I'm trying this method tomorrow.

Excellent suggestion, and sounds very likely except for one small detail: OP has a M20B25 (i motor) which lacks the cold start injector. ;-)

A leaking injector on the other hand.....

[Ruffian]

It's either a working or it's not kind of part. Not a "eh it kind of works but I think its going bad" part.

Maybe that's what you found, but I found different. For my pump, in my car, that I replaced. It took a week for mine to completely fail. In that time, after testing the whole fuel system according to the bentley, I replaced the fuel filter, swapped in a known good fuel pressure regulator, and did countless fuel pressure tests. I would drive the car for an hour, go into a store, come out and it would start right up. Go into another store, come out and the car wouldn't start. Wait a half hour or longer, and it would start right back up. Or, try to start it, it would really run bad for 10 seconds, then fire right up.

The only way I was finally able to find it was the pump was I got lucky enough to replicate the "non-working" time at home by taking it for a drive, coming home, turning it off, wait about 5 minutes and the try to restart it. It "only" took about 4 attempts to finally get it to not start. Kinda weird when you get in a car to start it, and it starts, yet you're disappointed. Diagnosing the problem, I had the terminals in the relay jumped and no pump activity(Naturally, you think bad fuel pump, but I had done this test countless times during the problem period and the pump would fire right up). Took out the back seat and with a multimeter was able to realize the lead was getting the signal. I bumped the fuel pump by accident and it fired right up. So for the next two days waiting to get a pump, I had the back seat out, and when it wouldn't co-operate and start, I had to tap on the top of the fuel pump with a screwdriver.

[PУCCKAЯ_e30ka]

can somebody elaborate on the engine temp sensor? what's the part #?

[dinanm3atl]

What about your cold start injector valve?
That could be your problem leading to over fueling at warm startup (smell of fuel).
Try leaving it unpluged next time you start your warm engine.
I get your exact problem too, and I'm trying this method tomorrow.

Yup :) I have an "i" motor so unfortunately won't be my problem!


With the pump my issue is this... I know how it works and how it functions but if it is not liking being "hot" then running it at a 1/4 tank it would have some problem while running or hell may even lock up while running? This issue happens with lots of fuel, low fuel etc...

This weekend I am going to play with it :( I worked on cars for a living so i hate diag now. I just like to replace parts and it works better hehe

[Doughnut]

Yup :) I have an "i" motor so unfortunately won't be my problem!

Oh?
Is there not a valve on the opposite side to the throttle body on the 325i intake manifold?
My 323i 6cyl has one with two wires going to it and a fuel line.

[rcko]

I have had this identical same issue with my 88 325is. I just replaced the DME temp ref sensor with a new one so I hope this address the issue. It is the same type of intermittent start specially on cool days but once every other week.

The other part to ck is the check valve on the fuel pump. This valve is suppose to help maintain pressure on the fuel line and thus prevent evaporation of the fuel due to heat soak. I read about this one in Bimmer Forums. The poster had similar sypmtons and apparently this $3 part fixed it.
The dealer will claim that the ck valve is not sold individually from the pump, but apparently this 5 series parts is compatible and does the same job plus is external to the pump.

If you dont hear from me again in this post assume the DME ref coolant sender was the fix. I will repost if the issue re-appears and let you all know if the checkvalve fixed it.

[dinanm3atl]

Part Number for what you bought for 3 dollars :)

My Engine bay

[rcko]

here is the link from bimmer forums

http://forums.bimmerforums.com/forum/showthread.php?t=734319&highlight=fuel+pump+check+valve

"16 14 9 068 988 current price looks to be $2.77"

http://www.bmwe34.net/E34main/Trouble/535ihot_start.asp <- procedure for an E34, but the same applies for the E30. Remove the rear seat bottom (pull up at the front) and the access panel on the P/S of the car to gain access to the top of the fuel pump. Make sure you get the proper line (pressure not return) when you install the valve.

more from bimmer forum

Diagnosis:

The check valve in the main fuel pump was leaking allowing the fuel injector rail residual pressure to
bleed off resulting in formation of a huge fuel vapor bubble in the fuel rail and back down the fuel line toward the pump.

The extra cranking time was needed by the fuel pump to recompress and
eliminate the fuel vapor bubble in the line and repressurize the fuel injector rail.

Installation can be anywhere in the fuel pressure line but next to the main pressure pump is best.

It is a two screw clamp job.












This part is basically just a lenth of hose with a check valve (one way valve).
You cut into the hose leading towards the engine from the fuel pump and use hose clamps (included in the kit) to splice this in.
I took the back seat out and spliced it in using the little access panel on the passenger side.
I wish I could be more descriptive but I did this over a year ago...hopefully that helps you.


Summary: This is an external check valve that is spliced into the fuel line.
This way, when you shut off the car, the line remains full of fuel,
so when it comes time to start the car again you do not have a long crank time waiting for the fuel to travel the length of the line."

[dinanm3atl]

Excellent

I think this is my problem! Getting new injectors next weekend with new pintle/o-rings/cleaned

[Doughnut]

Excellent

I think this is my problem! Getting new injectors next weekend with new pintle/o-rings/cleaned

edit.

[Doughnut]

How did you go with the injectors and check valve??

[dinanm3atl]

Well the check valve makes it WAYYYYYYYY better

Still a little rough sometimes.

Didn't have time to do the injectors. Will report back

[rcko]

coolant temp ref sensor did not fix it... so i have ordered the ck valve.

clean injectors will make it better ++

[rcko]

well the ck valve didnt fix it either, but I can now crank it longer when it vapor locks and starts up after about 3-5 seconds. Before it wouldnt even want to start till after 3-4 times of long cranking.

Guess I am left with the fuel pump or carbon canister Given I have replaced everything else.