Car dies after low fuel issue - fixed

[chazsandiego]

Was late for work and didn't have time to refuel before hitting the road. By the time I arrived the fuel light had come on. After my shift I hit the refueling station and head off but only get 5 blocks before my vehicles dies like it's out of gas. Weird, since i just refuelled. After maybe 30 minutes of waiting and priming the fuel pump car started up strong but only gets 2 blocks before dying. Starts again briefly and feebly but won't rev then dies and won't do anything but crank.

Replaced the fuel filter and plugs. Car eventually started strong but died after idling for 5 minutes or so. Eventually got it started back up, was able to drive a few blocks and let it idle for about 20 minutes before heading home. No immediate issues on the freeway for about 15 minutes, until the vehicle had a hiccup of power loss. By the time I had exited the hiccups were more frequent and my idle speed was jumpy. Car died immediately in park upon arrival at home.

So, new fuel filter is in the mail (Bosch) and I hope that's the end of it. But I'm very paranoid that it could be something more complicated. Any feedback is always appreciated!

(Side note: I drove this vehicle from San Diego to Las Vegas last month with no issues)

[shogun]

Can only be these items, fuel pump, fuel pre-filter at the bottom of the pump and the inline fuel filter.
Also check the fuel pressure regulator, pull off the vacuum hose and check if it is dry and no fuel inside, if fuel inside, the diaphragm of the fuel pressure regulator is broken.

[unity]

Mechanics say there are lots of "coincidences" with cars, this may be one and the problem unrelated to low fuel. Now if I had to bet, I would put more emphasis on it being the pump. With that said, everything you will be replacing should be when a new pump goes in anyway. Just good practice.

For the M70 I went with this pump:
http://www.ebay.com/itm/TRE-432-BMW-...-/332256863413

I have not had any apparent issues with them. Car runs good even at WOT. And unlike some, it was direct fit. If you are concerned about fuel pump prices, I suggest seeing if they have a compatible model.

[cirrusblau]

Pump filter may havee clogged when you almost ran it out of gas. The dirt may release itself when you turn off but stays in the baffle, then gets sucked again when you start it right up.

[unity]

^ Thats a misnomer. The pumps always suck form the bottom of the tank. Low fuel does not mean that for some reason debris will be sucked up. It physically makes zero sense.

[cirrusblau]

^ Thats a misnomer. The pumps always suck form the bottom of the tank. Low fuel does not mean that for some reason debris will be sucked up. It physically makes zero sense.

I know that, but those latent debris may entered the baffle when there was less fuel in it.

[whiskychaser]

Please excuse my pedestrian approach but before buying any new parts, I'd want to test the current fuel pressure and flow. I'd put a pressure gauge on and run the car. If pressure drops and then the car stops running, you have your answer. But that does not mean the pump is faulty or the filter is blocked. You could, for example, just have a dry joint on the fuel pump relay

[E32FAN]

shogun always reminds us that Fusible Link A can go intermittent and kill power to the the DME box.

You can conveniently check this at your D100 Diagnostic Connector, pin 14. The voltage should be 12V at all times. If it is low when cranking, then Fusible A is your problem.

Or the fuel pump relay, as whiskychaser posted.

[chazsandiego]

Update:

I swapped the fuel pump out and the car fired right up but i only had time take it around the block, with no issues.

Today however, after refuelling, and letting my vehicle idle while using the atm the vehicle died shortly after returning to the road. Pulled over, wouldn't start. Then started back up and had no issues the mile or so home.

Do i need to pursue this any further or was their just air in my line/tank from the pump swap?

Thanks Always!

[shogun]

There should be no air in the fuel line anymore, that goes out within a few seconds after starting the new pump. Check the fusible link A as described above by E32Fan, maybe it has a crack and sometimes works and sometimes not. It is located close to the battery and hidden in plastic wrap, pics are on my website https://www.bimmerforums.com/forum/s...2-fusible-link

[chazsandiego]

I was able to find a 100amp(too high?) inline fuse holder to replace fusible link A. Got everything hooked up, car started, sputtered then died and currently will not start back up. I had also made sure to double check my fuel pressure regulator. The vacuum hose (no clamps, just pulls off?) was dry and did not smell of fuel. I did not however remove the whole regulator to check for seepage. I will most likely pick up a new one today but I'm not extremely confident it will solve my issue.

As always any assistance has been and is still greatly appreciated!

Side note: while replacing the fuel pump I was unable to locate any solid info on what the "pre filter" looks like of how to replace/service although my blinders may not have allowed me to find any such info.

[shogun]

Vacuum hose on the fuel pressure regulator has no clamp.
The fuel pump pre-filter is located at the bottom = suction side of the pump, here some pics from the 750 pump change, tyhere you can see the filter, in case of your 735 there is only one pump
http://bmwe32.masscom.net/sean750/fu...t/Fuelpump.htm

[chazsandiego]

Thanks for the link on that pump write up. I definitely got a new pre-filter with the pump. I also spilled some gas just like in the write up (the smell goes away right?), and i also snapped one of those bolts off (not looking forward to that repair).

As for the fuel pressure regulator, I was checking the correct area and it seems okay but I am still going to replace it tomorrow morning. Other than that car did start up about an hour ago, but died again after giving it some throttle. I will update the forum tomorrow after I change that fuel pressure regulator.

Thanks as always!

[chazsandiego]

Quick update. Got the new pressure regulator on and although it sounds happier while running it is still cutting off after a few seconds.

One thing I neglected to check was the fuel pump relay which upon inspection didn't look great. I may be able to get one this afternoon but tomorrow is more likely.

Until then I am going to check my pump install job for errors.

Thanks always!

[chazsandiego]

After checking that my pump was indeed installed correctly I decided to try resetting the computer. Much to my surprise the vehicle started with no hesitation. The idle felt funny until I turned up the fan w/ac on which seemed to stabilize the rpms. I felt confident in the vehicle but decided to wait until I got the new fuel pump relay in.

This morning same deal, car is happier with AC on, even after the new fuel pump relay.

Car performs beautifully on the freeway (20 min drive). Exit the freeway, idle, stutter, drives fine, then dies while turning. Barely starts up now and dies immediately.

So kinda back to square one at the moment. My lifelong auto shop (sadly doesn't do bmw) suggested a Cam or Crank shaft sensor issue but it was an educated guess.

As always any and all thoughts or suggestions are greatly appreciated!

[shogun]

The crankshaft position sensor you can test.
Using digital multimeter, check resistance between terminals 1 and 2 in crankshaft position/rpm sensor connector.

Crankshaft Position/rpm Sensor Specifications
• Coil resistance (approx.) @ 20°C . . . . . . 540 ± 10% Ω
• Air gap (sensor distance from
toothed wheel) . . . . . . . 1.0 ± 0.3 mm (0.04 ± 0.01 in.)

http://www.bimmerboard.com/forums/posts/1072189/

and the donut on cylinder 6 you can also test. Here are all the data https://www.bimmerforums.com/forum/s...5#post29782435
any possibility that you can read out fault codes?
Also one other idea: might be also the DME unit, when it gets hot, it might fail. You could test another DME. But that is all just a guess, difficult to poinpoint

[chazsandiego]

I'll get my hands on a multimeter and check out those numbers.

As far as fault codes goes, I will give it the stomp test later. Hopefully I can rent a more sophisticated reader if one is available at the AutoZone.

As far as DME compatability goes I'm not exactly sure if I'm finding the correct part on realoem. If I am correct my local junkyard has more than enough vehicles that should be able to provide the necessary part. Here is the link I'm going off of for the DME

http://www.realoem.com/bmw/enUS/show...diagId=12_1605

I appreciate all the help! I'll keep you all updated. Thanks again.

[chazsandiego]

Accidentally deleted my last post.

Gotta get my hands on a new multimeter before I can check that out. Was able to stomp test but because I had attempted to reset the computer again (I think) I was only getting a 1444 reading. Also, i may be attempting to reset the computer improperly (vice grips and such). Will reattempt it with some proper cables. Will also try to rent a reader from autozone if available.

As for the DME, i was able to find this on realoem. Which shows I have a bit of latitude for the variety of vehicles I may be able to pull one from at the junkyard.
But I want to double check with the forum before heading down.

http://www.realoem.com/bmw/enUS/show...diagId=12_1605

The help is greatly appreciated!

[shogun]

For a 1990 E32 735 you need a Motronic for the M30, important is the Bosch number on the sticker.
735i/iL E32 M30/B35 86-88 0 261 200 150 Bosch Motronic M1.1
735i/iL E32 M30/B35 (211hp) 89-92 0 261 200 179 Bosch Motronic M1.3

for example E34 has the same one, 535i E34 M30/B35 89-92 0 261 200 179 Bosch Motronic M1.3

Check in the E34 for sale forum, maybe someone has one, south42 has a lot of parts and he just gives a special discount on parts as he moves to another place.

[chazsandiego]

Had some unexpected time with the vehicle today so I decided to pop the hood and listen for any unusual noises in the engine bay.

With the key in the 2nd position all the usual clicks and dings were in place. However after 5 or so seconds I discover my Idle Control Valve is buzzing like a florescent light fixture. Inspection of the valve shows that it is buzzing locked closed. Unplugging it allowed me to manually open the valve only to have it immediately close and buzz upon receiving power. I'd had an issue maybe two months ago with my ICV causing a rough idle in traffic and triggering my CEL..

I know it is merely wishful thinking to assume my ICV could be causing my no start/stalling issues. But I feel like it could lead me to the root of this problem.

Any thoughts or comments always appreciated!

[shogun]

if it does not buzz, it might be dead, you can test it, Bentley says: M30 without EML
before checking the valve, confirm that the throttle position switch works correctly. The test given below is an electric check only. it does not check the mechanical operation of the valve. if the valve is sticking, hanging up or is sluggish in operation, substituting a known good valve is the best way to check it.
On 735 with ASC traction control, an idle speed control valve is not used. Instead, idle speed is controlled via the EML.

with engine running, check that the idle control valve is buzzing.
turn on A/C or shift into drive. idle should remain steady or increase slightly.
if valve is not buzzing or if idle decreases, stop engine and disconnect harness connector from valve.
check resistance of valve across its terminals. test values are listed below.
idle speed control valve coil resistance values M30
terminals 1 and 2 20+/-2 ohms
terminals 2 and 3 20+/-2 ohms
terminals 1 and 3 40+/-4 ohms

if you suspect an intermittent fault, lightly tap the valve while testing resistance.

with valve harness connector disconnected, check for battery voltage at red/white wire in connector with ignition on.
If there is no voltage, check wiring between connector and main DME relay.

The idle speed control valve receives positive + battery voltage from the main DME relay.
if voltage is present as described above, check wiring between ECM and valve. If no wiring faults are found, check ECM output signal to valve.

also read this thread https://www.bimmerforums.com/forum/s...ttently-solved

[chazsandiego]

Was able to get back to the vehicle today for some trouble shooting and part swapping.

After locking my keys in the vehicle with my other car keys and cell phone I was luckily able to fashion a metal bucket handle into a coat hanger like device and was back into the vehicle.

Grabbed an ignition switch from the junkyard. While it has improved the performance of my dashboard warnings reader (only the top half functioned leaving letters cut off).
Put that in as well as a new main relay and was still unable to get it started.

When the vehicle died this most recent time it was suggested that a crank position sensor could be the culprit. New one arriving tomorrow. From what i could see the old one looked pretty cruddy. I noticed that the harness is connected in proximity to where my previous radiator hose exploded and steam cleaned my engine bay. If that crank position sensor is the problem im guessing that hose issue probably contributed to it.

\\Rechecked my fuel pressure regulator and found that the clamped hose which had previously doused me in fuel when i replaced the old one was completely dry.

Ill get to that crank position sensor tomorrow and hopefully will have some good news!

Thanks as always for all the assistance

[chazsandiego]

New crank position sensor and the car is back to life!

Old one was filthy! Tried cleaning before replacing, no luck.

Paranoia drove me to travel 45mins to grab a compatible DME just in case (only $60).

Car is idling with no issue however the throttle feels like it's lagging initially during acceleration.

I'm resetting the computer now to see if that helps. Then a brief test drive!

Much thanks for all your help Shogun and the rest of the forum. I greatly appreciate your patience with my caveman approach to vehicle repair.

[CamE32]

New crank position sensor and the car is back to life!

Old one was filthy! Tried cleaning before replacing, no luck.

Paranoia drove me to travel 45mins to grab a compatible DME just in case (only $60).

Car is idling with no issue however the throttle feels like it's lagging initially during acceleration.

I'm resetting the computer now to see if that helps. Then a brief test drive!

Much thanks for all your help Shogun and the rest of the forum. I greatly appreciate your patience with my caveman approach to vehicle repair.

Any update on your saga? I’m at the point of replacing my DME due to same issues in cold weather (ONLY cold weather, after it warms up). Curious if the CPS solved your issue, or the new DME? Or neither…?