1990 BMW E30 325i - Trouble Starting after Car sits overnight

[chomowitz]

I have a 1990 BMW E30 325i. Recently I have had starting problems. It seemed to come on all at once.

The symptoms are that, after the car has sat for a while, the car turns over (battery and starter okay), but does not start. If I let it continue to turn (10 - 15 seconds), it eventually starts (but reluctantly). After it starts ... If I turn it off and retry starting immediately, it starts right away. When driving ... The engine seems to run fine (no sputtering, hesitation or lack of response). The problem is centered in that first start after sitting for a while.

I have done some reading and have tried the following ...
1) Replaced E30 Main ECU and Fuel Pump Relays
2) Installed external fuel check valve at Fuel Pump (under rear seat).
3) Replaced Distributor and Rotor
4) Inspected, cleaned and gapped spark plugs.
5) Checked and cleaned air filter

None of of these solved the problem. After I switched the relays (1. above), the problem seemed to go away, but it then returned a day or two later. I should also mention that the problem seems to be getting worse. Initially there were days when it would start right up in the morning. Now the problem seems to be there everyday and often after sitting for hours. Note that I live in a warm climate (FL), so being cold due to outside temperature is not an issue.

If someone could give me step by step troubleshooting from most likely to least likely, I would appreciate it.

Thank you in advance for your support ...

[superj]

does it lose fuel pressure when sitting for a bit? I see you added a check valve at the fuel pump side but is the regulator leaking out slowly at the rail?

[chomowitz]

Hey superj ... Thanks for the input. I am trying to figure out how to test for fuel pressure (I have no pressure gauge). I added the check valve based upon something that I read re: starting problems like mine and this youtube video ( https://www.youtube.com/watch?v=6ezt4M1NZDk ). It made sense that if the check valve in the fuel pump was faulty, fuel could be running back into the tank when the car sat so that it had limited fuel on the first start. After I added the external check valve, the first start problem remained.

Re: Your question of the regulator leaking fuel slowly at the rail? ... Can you clarify how I test that? I am suspicious that my first start issue is related to fuel, but I'm struggling on how to test. Do you have ideas on tests I should perform?

[superj]

take off the vacuum line and see if any fuel dribbles out after turning the car off. if not, the rest of the test need a gauge from the auto parts place because that would tell you if there is a leak after the check valve, like a fuel injector or something else.

I would have thought that check valve would fix it since most of the time, that is the issue, but maybe yours is an injector or regulator? I know if its the regulator, it will sometimes leak from that vacuum line connection but the other leaks, are harder to pin point so its easier to just use a gauge.

I would say maybe a vacuum leak in the intake but then it would be tough to start each time, not just after sitting.

[chomowitz]

Pardon my ignorance, but when you say "intake", what are you referring to?

[chomowitz]

Superj ... I disconnected the vacuum line to the Fuel Pressure Regulator and no fuel dripped out? From your suggestion, I will need to get a fuel pressure kit and check the fuel pressure. I found another website that talks about checking the fuel pressure ... https://www.bimmerfest.com/forums/sh...d.php?t=308443 . I'm going to see if Autozone has a loaner fuel pressure kit.

[superj]

intake manifold, sorry

[chomowitz]

I disconnected the vacuum line from the fuel pressure regulator and no fuel trickled out (ignition off). I assume that means it is not leaking. Can it be stuck? Could that cause my "first start problem?

Also, I'm looking into getting a loaner fuel pressure kit from Autozone. From my reading, I could monitor the fuel pressure 1) at start up, 2) while running and 3) also monitor if it holds after turning car off and letting it sit.

[superj]

yes, do those checks and the regulator not leaking when the line is disconnected means that the diaphragm is good but it could still have an issue. do the loaner gauge tests though and it will tell you more.

[chomowitz]

I just ran a fuel pressure test. I put a T in the line to the fuel rail and attached the gauge off the T. NOTE: when I detached the line to the fuel rail, there was fuel under pressure. I had driven the car to pickup the test kit and returned. The disconnect occurred within about 15 minutes after I got back.

Re: the first test ... The gauge read 36+psi while the engine was running. I let it run about a minute, then shut it down. After about 45 minutes, the reading had drifted down to 26 psi. I went back to be sure that the hose clamps and fittings to the gauge were all tight and then restarted the car (it started right up)... The pressure went right back up to 36+ psi.

Does the dropping pressure indicate that the FPR is bad? I assume the the external check valve I installed at the fuel pump isolates the pressure loss between the check valve and the pressure gauge.

Also, did I mount the T/Gauge in the right place? Should I T into the regulator instead?

Any thoughts?

[chomowitz]

I did another fuel pressure test.

I got the car to start and let it idle for a few minutes. While idling, the pressure read 36-37 psi. I then shut it down and monitored the pressure. Below is a table of what I found ...
Car shutdown ~37 psi
+ 27 minutes 32 psi
+ 39 minutes 28 psi
+ 44 minutes 26 psi
+ 67 minutes 20 psi
+ 93 minutes 18 psi
+105 minutes 16 psi
+133 minutes 0 psi

Another observation ... When I tried to restart, I'm pretty sure that fuel did not start to run until after letting the starter crank for 15 - 20 seconds. I measured the voltage on the fuel pump relay's pin that goes to the fuel pump and it shows 12 volts with the ignition key turned to start (i.e. cranking), but I didn't hear the fuel pump buzzing. Do I have two problems?

[superj]

that's weird. if its getting 12v than I would imagine it should vibrate. you can take the line that points towards the driver's seat, the one that is curved metal, and pop the rubber off and put a bit of line into a container and then turn the key to see how fast the fuel comes out. that is the pressure side of the pump

- - - Updated - - -

and the loss of pressure is why it takes long to start after sitting for a while

[chomowitz]

Okay ... I disconnected the rubber fuel line and put a line into a container from the fuel pump. When I turn the key ON (not to the cranking position), no gas flows at all. When I turn it to the start/cranking position, I immediately had fuel flow into the container. This indicates that the issue may be that because the fuel drains back into the tank, the fuel line to the engine needs to refill before the engine can actually start. Any comments?

Also, while I had it disconnected, I tested the external check valve I had connected and I found that when I blow into it in the direction it is supposed to block, there is air passing through. When I first put the check valve in, I expected it to fix the problem, but it did not. The fuel pressure test data I sent earlier made me suspicious that the check valve was not blocking the fuel from draining back into the fuel tank. I decided to remove the check valve and return it (already done). I'm now wondering if there is a check valve that works reliably because most of them look the same (this is the one I bought http://www.amazon.com/Muzzys-Non-Ret.../dp/B01LY7WD50 ). If I do not put in an external check valve, I think that I will have to replace the fuel pump (where the original check valve was). Does this make sense?

After sending this, I plan to reconnect the fuel pump in its original configuration (no in-line external check valve). I suspect that the fuel pressure test will show the pressure dropping after starting and then shutting down the engine ... I'll report on this after it is done.

[superj]

your thought on it needing to fill the line is correct. that's why it takes long to fire. It has to fill the line, then get it up to pressure. and it does only start pumping when the engine is turning, not in the run position of the key. it is a safety deal where if the engine is not turning, it stops fuel so if the car gets in an accident, the pump doesn't keep fueling a possible fire.

on the check valve, there are, but they cost a bunch. I noticed while researching check valves for our same issue, they guys who bought the higher cost ones that are brand name from jegs, or some place like that, didn't have the failure rate like yours (and I think mine) have. I noticed the 86 325e we put one in is taking longer and longer starting again. and yes, to fix it will require a new pump.

[chomowitz]

I am still monitoring the fuel pressure after starting the car and turning it off. the fall off in the initial 20 minutes was faster that with the external check valve in there. I'm still watching it.

I have read elsewhere that the fuel injectors can be a cause of fuel pressure dropping. I assume that would mean that fuel is leaking through the injectors into the engine chambers. If that were the case, wouldn't I see discolored exhaust when it started? I haven't seen that to be the case. Are there things I can check to verify that the pressure drop is not due to leaky injectors?

[superj]

fuel injectors can drip, or dribble fuel when the car is off. I think most of the time it runs down the cylinder walls and dilutes the oil, if its a bad leaky injector. otherwise, you might not ever see it because to go from pressurized to unpressurized doesn't take a lot of fuel loss

[chomowitz]

Some confusing events today.

Here are the sequence of events from yesterday and this morning before I started the car again ...
1) Yesterday afternoon, I decided to remove the external check valve and return it. As I was removing it and restoring the connection to the original configuration, I noticed that the fuel pump was loose (rotated when I was restoring gas line connections). I attempted to pull it out with no success. I had not removed the sender unit. I rotated it back and forth and then rotated it as far as I could clockwise (tightening).
2) I then started the car and was surprised that it started normally. I let the pressure build up (~36-37 psi). I then monitored it. The table below is what I saw ...
36+ psi at shutdown
34 +2 minutes
32 +4
30 +18
28 +26
27.8 +32
21.8 +80
At this point I decided to put a clamp between the fuel rail and the pressure gauge to see if it continued to fall. I had read that this test might tell you if the injectors were the problem, the theory being that if the pressure falls with the clamp on, then the injectors may not be the problem. I continued to monitor the pressure with the clamp on ...
20 reading after clamp install
18 +16 minutes after clamp install
16 +48
~9 +174
0 first thing this morning
3) I needed to run an errand, so I removed the fuel pressure connections and restored the original fuel line connection to the fuel rail.
4) I assumed that all the fuel was out of the fuel line and that the car would struggle to start and require 10-15 seconds of cranking. To my surprise it started right up. I turned it off and tried again and again it started right up. I ran my errand and when I started the car after doing my shopping, it started right up.

When I found the fuel pump was loose and rotated it back and forth, could I have jarred something that is now working?

Right now, I am letting the car sit (no fuel gauge, no external check valve), so that I can see if it starts right up again.

Any thoughts?

[chomowitz]

By the way ... When restoring connections at the fuel pump, I noticed that the 2 prong electrical connector to the pump was deteriorating (bits of plastic breaking off). I have not been able to locate a replacement. Information on where I can get a replacement will be appreciated ...

[superj]

no idea on the connection replacement but that will be awesome if the pump being loose was the only problem

[chomowitz]

After my last update, I let the car sit for about 6 hours. When I then attempted to start it, it struggled to start for 10+ seconds. Problem still there.

Last evening, I reinstalled the pressure gauge, but I put a flow valve between the gauge and the fuel rail. The intent was to verify that injector leakage was not the problem.

I started the car (it struggled) let the pressure stabilize (36+ psi), shut car down and immediately turned the valve off so that the pressure gauge was only monitoring pressure between it and the fuel pump. The result was that the pressure dropped to zero over 45 minutes. I then repeated the test, but left the valve open (pressure gauge monitoring both fuel rail line and line to fuel pump). The results were the same.

At this point, I believe the problem is the check valve in the fuel pump. I could take a chance and find another external check valve that "might" work or get a new fuel pump. I'm thinking the better path is to get a new fuel pump.

Any comments?

[superj]

yes sir, it probably is the best way.

I used a fuel pump form a 76 chevy vega on one of my e30s. it fit and must have a check valve because the car starts almost immediately. I had to reuse the old mount assembly and stuff and just swap the pump motor, which this one was a little longer but everything fit and works. I did it as a test because I had read you could swap them and it was readily available at the local parts place.

but, rock auto has pump motors from 25 to 112 and complete pump with housing assembly for 80 to 150 so its not expensive to just do the whole thing and be good to go with a drop in replacement

[chomowitz]

By the way ... I found a replacement connector for the two prong connection to the fuel pump ... http://www.ebay.com/itm/BRAKE-MASTER...3/372039090499 . Though this says it is for the brake fluid sensor, it visually matches the one on the fuel pump. FYI, the same connector is used on the coolant reservoir sensor as well.

[superj]

at least you found one. a bit ago someone had said where to buy all kinds of connectors but I cannot remember where they said to go

[chomowitz]

If you remember ... Let me know. I have other connectors that are or have disintegrated.

[superj]

ok

- - - Updated - - -

I searched for that post and the person said if you take the part number for the connector, from realoem.com, and go to the dealer, they are usually still available