Please help- M52 OBD1 E30 hesitation and issues starting.

[redrocket328]

Found this issue this weekend. I swapped the fuel pump out of my racecar (Walbro 255) which is obviously much stronger. Shortly after that was when the car stopped running completely. I checked the fuel pressure everywhere and ended up checking it right out of the pump. Turns out it was only pushing about 20 psi everywhere. Pulled the pump back out and the 2" rubbing hose connecting the pump to the housing complete blew apart right down the middle.

My theory is that the issue we were having before was that there was a smaller hole or tear in that hose which was preventing the fuel pressure from completely building up.

I replaced rubber hose on housing and car is back in action.

[rightcoastbias]

Yes I am running that exact setup.

I would check the speed sensor. I had a E36 M3 S52 for a while and had a similar hesitation on WOT pulls and ended up being bad speed sensor in diff. I called a very well know mechanic in the area that builds these cars and engines and that was his first guess so I would assume its a common issue. He was right.

My diff speed sensor is good, as my odometer does work. But my speedometer does not work. I'll try reflowing the solder joints and see if this changes anything.

Thanks.

Resolved:
I removed my cluster to reflow solder on the speedometer and found my CEL lamp was burnt out. Did the 5-stomp code read and found I had an Intake Air Temp CEL. My air intake temp sensor wires were torn off inside the plug. Reconnected wires to IAT. Car is pulling strong and the speedometer works. I'm giddy like a schoolgirl.

[redrocket328]

OP: You are (also) running a 2.8 liter engine (M52B28 with M50Vanos head) with a 2.5 liter engine map (413 ECU)?

I'm running the same setup you described. I've experienced a noticeable hesitation on WOT 3rd gear pulls. I haven't checked into it yet, because other than that, it runs fine. I guessed it was fuel pump/fuel filter/regulator or O2 sensor.

Yes I am running that exact setup.

I would check the speed sensor. I had a E36 M3 S52 for a while and had a similar hesitation on WOT pulls and ended up being bad speed sensor in diff. I called a very well know mechanic in the area that builds these cars and engines and that was his first guess so I would assume its a common issue. He was right.

[rightcoastbias]

OP: You are (also) running a 2.8 liter engine (M52B28 with M50Vanos head) with a 2.5 liter engine map (413 ECU)?

I'm running the same setup you described. I've experienced a noticeable hesitation on WOT 3rd gear pulls. I haven't checked into it yet, because other than that, it runs fine. I guessed it was fuel pump/fuel filter/regulator or O2 sensor.

[BBDirtbiking]

And everyone wonders why i harp on OBD2 so much. Youd never have this problem with it.

How so?

[redrocket328]

have you check your speed sensors on the diff and making sure your ECU is getting a signal .. i have a 87 325is i was having a similar problem an ended up being my speed sensor my ecu was not getting a speed signal... i had to run 2 wires from my glovebox to cluster.. if i remember correctly... its been 2 years from my swap....:D

It would really affect it that much, even at idle? I cannot guarentee it is getting signal. Atleast, I havent wired it up and the speedo on the cluster doesnt work.... I just thought it was another shotty E30 cluster but maybe.

What needs to be done to get the ECU signal? In the mean time Ill do some research on it but if you could send me your experience and what you did, that would be great.

[isra]

have you check your speed sensors on the diff and making sure your ECU is getting a signal .. i have a 87 325is i was having a similar problem an ended up being my speed sensor my ecu was not getting a speed signal... i had to run 2 wires from my glovebox to cluster.. if i remember correctly... its been 2 years from my swap....:D

[328ijunkie]

And everyone wonders why i harp on OBD2 so much. Youd never have this problem with it.

[redrocket328]

update: as of today, the car wont start at all. it will crank and crank and wife once but then stops cranking and wont fire beyond one initial fire, if it fires at all.

[redrocket328]

Which injectors are you using? you said the 413 ecu with stock chip is giving you trouble. that's for #17 but m52 uses the pink top #21.5. it's possible that your engine is choking on fuel. the m3 ecu you tried was for s50 or s52? i would suggest to get the right tune for the engine before you go into serious troubleshooting.

The head and all components along the head are off of M50 so im assuming injectors are from m50 but i will confirm that this week. Also, m3 ecu was from 95 which is s50

[treff-7]

Which injectors are you using? you said the 413 ecu with stock chip is giving you trouble. that's for #17 but m52 uses the pink top #21.5. it's possible that your engine is choking on fuel. the m3 ecu you tried was for s50 or s52? i would suggest to get the right tune for the engine before you go into serious troubleshooting.

[MaxBell]

I have a similar sounding problem, but I'm not as far along in my diagnosis. Temp sensors are coming soon for me.

Good luck man! DON'T GIVE UP!!

[redrocket328]

Forgot to add this in the thread but I actually swap ECU's as well. The ECU was from a 95 M3 but should work. It started and gave all the same issues. The chip in the M3 ecu is a turner chip but 413 ECU is running stock chip.

I unplugged vanos as well and still had same issues.

I pulled grounds off and checked everything cleaned and reattached but I havent actually changed ground wires.

I am thinking it is something electrical. Has anyone heard of issues like this being caused by voltage regulator possibly?

[cormier]

as stated you seem to have covered your bases pretty well :S

Also curious about ECU--running the stock tune now or some chip?

Tried swapping injectors? FPR is hooked up ok? Nothing obvious clogging the TB or MAF?

any other odd symptoms? especially electrical? youre SURE the grounds are all ok?

just shots in the dark I know...

[treff-7]

when i started to read your post i had a few ideas but slowly you ruled almost all of them out.
to me it seems like you either have a bad connection, damaged wire or a sensor going bad but the harness is replaced, cam and crank sensors are replaced so there is little chance to that.
i was also thinking the ecu if it has the right chips for the engine/injector combo but it would be either bad or good. not moody like yours.
my last guess would be the vanos. have you tried to disconnect it and see how it runs without it? maybe it's sticking or the actuator is going bad.