Starting problem

[Ari Ehu]

Hello. I am new here.
I have a starting problem with my E30, 316i with an m40b18 motor in it.
The problem I am having is, when I turn the key over to start the engine, all I can hear is the starter motor cranking for a while. Although sometimes it will take a few cranks before the engine comes to life. Sometimes it takes maybe 3 or 4 goes before it starts up. I am wondering if it might be a fuel problem. Any help would be greatly appreciated. Thanks.

If a video is needed I can provide one. Cheers

[e30onBBSs]

Probably dropping fuel pressure. Could be a number of things- Leaky injector, bad check valve, clogged filter (least likely). Hook up a fuel pressure gauge and see if it loses pressure. You have to check in a couple different spots to determine which area of the vehicle is at fault if it does lose pressure too rapidly. It shouldn't lose much pressure at all- like a couple psi over a long time.

[Ari Ehu]

Probably dropping fuel pressure. Could be a number of things- Leaky injector, bad check valve, clogged filter (least likely). Hook up a fuel pressure gauge and see if it loses pressure. You have to check in a couple different spots to determine which area of the vehicle is at fault if it does lose pressure too rapidly. It shouldn't lose much pressure at all- like a couple psi over a long time.

Hello, thanks for the reply.
I have serviced and changed the fuel filter, spark plugs. Etc. I have reason to think it might be the fuel pump but I am unsure how to test it. The problem almost feels like there isn't fuel in the engine when I'm cracking the starter motor, so there isn't any thing for the spark plugs to ignite. How would I go about checking a leaky injector and check valve?
Cheers

[roguetoaster]

Sounds like the fuel pump check valve to me. You could check for it either at the fuel pump, your M40 pump is probably single outlet, so it will be easy to pull the correct line and check if it still has fuel in it, or in the engine bay with the same method. Be aware that if the fuel pump is not the issue you may be subject to fuel spray wherever you are working, so disconnect the battery and protect your eyes.

On the check valve front, a factory fix (but for later 5/7 series perhaps) used to be available, but was NLA two years ago when I faced this issue. So I went with a 5/16" NB brass check valve with Viton seals, and installed in right next to the fuel pump outlet. Cost was something like $20 shipped + a tiny section of high pressure fuel line and 2x fuel line clamps.

One leaky injector seems less likely to cause that issue to me.

[Ari Ehu]

Sounds like the fuel pump check valve to me. You could check for it either at the fuel pump, your M40 pump is probably single outlet, so it will be easy to pull the correct line and check if it still has fuel in it, or in the engine bay with the same method. Be aware that if the fuel pump is not the issue you may be subject to fuel spray wherever you are working, so disconnect the battery and protect your eyes.

On the check valve front, a factory fix (but for later 5/7 series perhaps) used to be available, but was NLA two years ago when I faced this issue. So I went with a 5/16" NB brass check valve with Viton seals, and installed in right next to the fuel pump outlet. Cost was something like $20 shipped + a tiny section of high pressure fuel line and 2x fuel line clamps.

One leaky injector seems less likely to cause that issue to me.

Hey man, thanks for the reply.
What your saying is disconnect a fuel line from the fuel pump and test to see if it is flowing???

Any chance you might have photos and a link of where I can buy the set you had purchased?

Cheers

[roguetoaster]

Hey man, thanks for the reply.
What your saying is disconnect a fuel line from the fuel pump and test to see if it is flowing???

Any chance you might have photos and a link of where I can buy the set you had purchased?

Cheers

Yes, after the car is off, battery is disconnected, and you have protected your eyes.

http://www.ebay.com/itm/5-16-HB-x-5-...-/231489096143

[Ari Ehu]

Yes, after the car is off, battery is disconnected, and you have protected your eyes.

http://www.ebay.com/itm/5-16-HB-x-5-...-/231489096143

Awesome man!
I will give that a go when the weather clears up.
Any chance you might also have photos of how you installed it?
Which line is the feed and return?

[roguetoaster]

Took some just for this thread.

M40s may have a different pump, maybe a single outlet.

[Ari Ehu]

Took some just for this thread.

M40s may have a different pump, maybe a single outlet.

Really appreciate it man, now I get the idea.
I do have an update to add. I am driving my car right now, it did start bad, took 2 cranks to start it. Once out I was driving on a straight then the revs dropped from 2k to 1k instantly in 4th gear, then bounced back up on its own. Then I came to a stop at an intersection, rolled in at 3rd, shifted down to 2nd and it stalled. it has happened before but the other time it seems as if it stalled, no revs nothing, then all of a sudden popped back up and threw the car. Hopefully that gives a bit more details.
Cheers

[roguetoaster]

Sounds more like a fuel (maybe the pump) or spark issue.

Test pressure, check spark, inspect the plugs for signs of lean operation.

[Ari Ehu]

Sounds more like a fuel (maybe the pump) or spark issue.

Test pressure, check spark, inspect the plugs for signs of lean operation.

Hey man. Been really busy lately so haven't gotten around to checking it. I'll give it a go sometime tonight, I let my friend in on what's happening and he has reason to suspect it could be something as simple as a bad filter on the fuel pump. As I had a leak coming from the fuel tank, because the fuel pump o ring was buggered, so I may also check that too.

[roguetoaster]

Hey man. Been really busy lately so haven't gotten around to checking it. I'll give it a go sometime tonight, I let my friend in on what's happening and he has reason to suspect it could be something as simple as a bad filter on the fuel pump. As I had a leak coming from the fuel tank, because the fuel pump o ring was buggered, so I may also check that too.

I suspect if the screen on the pump were clogged you would not be driving the car. At least it does not take much time to look at it, nor does it prevent you from using the car.

[Ari Ehu]

I suspect if the screen on the pump were clogged you would not be driving the car. At least it does not take much time to look at it, nor does it prevent you from using the car.

Do you think it could be a possibility? Although I will check either way.

[Ari Ehu]

Yes, after the car is off, battery is disconnected, and you have protected your eyes.

http://www.ebay.com/itm/5-16-HB-x-5-...-/231489096143

Hey just got around to buying the check valve, it doesnt ship to my location, any other options i can go with?
Just to add, is this one similar? https://www.trademe.co.nz/motors/car...1428577610.htm

[Kershaw]

Those check valves look right to me.