'84 318i no start - my winter beater with a heater

[vandy]

Hey all - I shoved the winter beater in the garage this weekend and tore into it to get it running again. It's a '84 318i, previously a one owner car given to me by the widow of my deceased friend Ken. I know, cool story bro.

When I parked the car last season, it was fighting typical surging idle problems. I shut it off one day and it wouldn't start the next morning. Cranks but no fire. I knew that the fuel pump was original so I said "screw it, I'll fix it next fall." So, welcome to next fall (ahem, winter)!

I pulled the fuel pump and the tank is full of rust. Eff. It sat for over 5 years with a half full tank, so no wonder. Anyways, I wanted to convert the car to a late e30 fuel system with an in-tank main instead of transfer + in-line main. So I followed this guide:

http://www.m42club.com/forums/showthread.php?t=9856

and then this guide:

http://www.e30tech.com/forum/showthread.php?t=106154

Old pumps out, new fuel line in, fuel supply and return lines swapped in the bay on the frame instead of on the pump bracket. New fuel filter too since I'm currently running a 1:1 of gas:rust (it's not really so bad that there is floating rust, but there IS rust present.)

So I crank it and I still have nothing. No start and no fuel pump priming. After a bit of reading, I see that the coolant temp sensor needs to send signal to the DME to send power to the pump. I have three known-working e30 fuel pumps in my garage and all three didn't prime on ignition.

I'm thinking I have a bad DME, or a bad coolant temp sensor. When it ran last year, I had a horrible high idle also. I have a new ICV and all new vacuum lines. The intake boot needs replaced and the AFM is dirty but not enough to push my idle to 3.5k, I don't think.

Other thoughts for me to check out?

Thanks everyone!

UPDATE:

I installed a new coolant temp sensor, as the jetronic looks to that for signal before sending signal to prime the pump. Weird, but apparently they fail regularly? I installed a new cap and rotor. Went to start, still no start and no fuel pump priming.

Getting frustrated, I ran wiring from a battery to the fuel pump power to get it pumping. Pump kicked on, I let it sit for about 10 seconds, then attempted to start the car. Still no start. So it sounds to me like I have two issues here, one of which is no fuel pump prime and another is fuel delivery.

The gas tank has a good bit of rust in it. It's my winter beater so I don't really care about it too much, but there could be a chance that it's clogged the metal fuel line running along the driver's side. When I get home from work today, I'll pull the hose at the firewall and prime the pump with the battery to see if I've got any fuel being delivered.

At this point, I guess my best guess is bad DME. Any thoughts?

[thebutterson]

Try jumpering the fuel pump relay pin 30 to 87b and see if the fuel pump primes.

[glnr13]

i agree with thebutterson. also check your fuel pressure regulator

[vandy]

Try jumpering the fuel pump relay pin 30 to 87b and see if the fuel pump primes.

Yes, it does. So dead fuel pump relay?

Also, I began tracing my guessed fuel starvation problems. Caught it all the way to the back of the car where the old main pump used to be. Popped both the rubber feed and return lines off the hard line and aimed them in a canister and then cranked the car with the pins jumpered and I had no fuel coming out. So I guess I have a clog somewhere above/in the tank?

[thebutterson]

Clean all the grounds in the engine bay, then reinstall the fuel pump relay and see if they prime. If not, get a new relay. If you can hear the pumps running, and there is gas in the tank, then you have a clog. The in tank pump is super easy to pull and check. It's under a panel under the passenger seat. Be absolutely sure you have enough fuel in the tank before you go ripping everything apart, there are guages that don't read correctly.

[vandy]

Clean all the grounds in the engine bay, then reinstall the fuel pump relay and see if they prime. If not, get a new relay. If you can hear the pumps running, and there is gas in the tank, then you have a clog. The in tank pump is super easy to pull and check. It's under a panel under the passenger seat. Be absolutely sure you have enough fuel in the tank before you go ripping everything apart, there are guages that don't read correctly.

Thanks for the reply! Up there ^ you'll see that I've already pulled the in-tank pump and replaced it with a new main in-tank from a late e30. New relay is on the way. I put a fresh 5 gallons of fuel in the car before diving into this project, but good call on the fuel level! I am going to pull the feed line off at the in-tank pump and at the hard line where the former main in-line pump was and pour some lacquer thinner in there and see if it can do some magic paired with some compressed air.

[Cyrix2k]

does the m10 have a crank sensor?

[jeffnhiscars]

... pour some lacquer thinner in there and see if it can do some magic paired with some compressed air.

Probably not the best choice given how volatile lacquer thinner is...and its ability to melt plastic

[vandy]

Probably not the best choice given how volatile lacquer thinner is...and its ability to melt plastic

It's only in there for a few seconds and I cleaned with brake cleaner and compressed air afterwards. If you have a better solution, then I am all ears!

does the m10 have a crank sensor?

Nope, but good thought.

[vandy]

The car is running again. My cocktail of fixes that got it running was

- new fuel pump relay
- new coolant temp sensor
- fuel pump wiring that correctly matched pos & neg so the pump wasn't blowing bubbles into the tank :rofl:

Thanks for the help, all!

[irish44j]

doh!