Rebuilt M42 318i fuel filter leaks on crank

[joncunanan]

I didn't touch the fuel pump or the fuel filter during my rebuild. When I crank to try to pump the oil, I removed the spark plugs, fuel relay and the fuel pump fuse #11. It pumped the oil just fine and no leaks. I put the spark plugs, relay and fuse back and it starts leaking on crank. I removed the fuel pump fuse again to check and it didn't leak.

I don't think the fuel filter or fuel pump was installed incorrectly as it was running fine before the rebuild.

My question is if I didn't touch the fuel pump or fuel filter during my rebuild, is it leaking at the fuel filter only when it pumps because a hose maybe cracked or rotted? Or is is it something like the fuel injectors causing back flow to the filter, flooding it?



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[superj]

only way to tell is if you get under and check. it could very easily be cracked lines

[joncunanan]

@superj. i was chatting with coworker and he told me that it could be that since the fuel was sitting in the gas tank for over a year, that gas being pumped is clogging the fuel filter, could this be the reason?

[superj]

it could have turned to varnish and the filter is gummed up

[joncunanan]

it could have turned to varnish and the filter is gummed up

it's been sitting for maybe 18 months, and it's been in the garage so i didn't think it would get that bad, but it's worth a shot. if i disconnect the fuel filter off the car, would it be a clear sign of the gas being gummed up clogging the filter?

i am thinking this is why the car cranks but no start as fuel is not getting to the injectors? the previous owner replaced the fuel pump a few months before i bought the car off him and it ran fine til the headgasket went out that prompted the rebuild. replacing the fuel filter is cheap enough if i have to, but the sending unit and/or the pump is expensive.

can the fuel injectors/fpr regular be ruled out? i just replaced the fpr hose and fuel hoses to the rail under the intake since i was already in there. could bad injectors push fuel back to the fuel filter and not allow the car to start?

[superj]

if you undo the two 10mm bolts holding the fuel pressure regulator on the end of the rail, does fuel come out when you turn the key?

[joncunanan]

I got under the car this weekend to get a closer look. it looks like there is a crack in the hose behind the filter going towards the rear of the car. I took our the rear seat to get to the access panels for the fuel lines and tried to see if it's leaking anywhere there but it looks dry.

I remember reading online that when you turn the key right before you crank you should hear the fuel pump "humming" to "prime". However I did not hear anything.

I removed the upper intake and to like the rail up and see the injectors and they were dry. The fuel hose on the left that goes to the black hard line started to hiss and spray out gas. I tightened down the hose and it stopped but that tells me there is fuel getting up to the rail. Does this mean the fuel pump is working?

I am still having problems getting the car to start. I pulled out the spark plugs and then cranked while it laid on the intake to check for spark and they all get spark.

My guesses:
1. Fuel not getting to fuel injector due to lack of pressure from either bad fuel pressure regulator, fuel pump, injectors, bad wiring, or all of it?

2. I put back the upper intake on and ran a stomp code test and got a 1216 code which is the Throttle Position Sensor. Would this prevent start if the fuel system was good?

3. Crank Position Sensor?

Damn, I thought I was almost there but this is starting to feel like another big side project if I gotta work on the fuel system but glad for these forums to guide me.

Thanks in advance.

[joncunanan]

Weird. I went to reply and Tapatalk created a new thread sorry.

[richardodn]

Threads merged.

FYI, the fuel pump does not "prime" on these cars. The Motronic ECU does not turn on the fuel pump until it sees timing data from a rotating engine.

Here's a quick description of the fuel system on the 92. Fuel is supplied from the tank at pressure with the internal pump. Supply is routed to the fuel rail passing through a fuel filter on the way. If you were seeing a little spray on that connection, that means the fuel pump is running. That also implies the pump relay and crank position sensor are working. The return path goes from the rail, through the fuel pressure regulator and then the return line back to the tank.

So back to why won't your car start. It sounds like you're getting fuel to the rail but the injectors may not be firing. I'd be looking at the engine harness connection below the intake manifold for corrosion.

[joncunanan]

Thank you for merging the thread.

I did the "mess under the intake mod" and no corrosion found.

Is there a way to test the fuel injectors are working while in the car and still on the rail to test the wiring?

[richardodn]

Yes, a noid light. You can usually get a free rental from the big chain auto parts stores. Youtube has videos on how to use them. I believe the M42 injectors use a Bosch (type 1) aka EV1 style. You can also pick up a kit on Amazon or Harbor Freight. It's unlikely they all went out, but not impossible.

Basically you're trying to verify
1. Fuel - you may want to simply pull the rail and injectors off, stick the ends of the injectors into individual bottles and crank the engine. You'll know for sure if they're firing.
2. Spark - There are many ways to check for spark. Cheap and easy is to pull a plug wire off the #1 plug. Stick a screwdriver in there. Grab the screwdriver by the insulated handle (would hurt to use a glove too) and hold the shaft about an 1/8" from ground. Have someone crank it and you should see a spark.
3. Air - Just check for intake side leaks.

[joncunanan]

If I pull the rail to test if the injectors spray and put bottles under each of the injectors, is it safe to crank with the upper intake and throttle body removed?

[richardodn]

Yes. Just be sure the injector retaining clips are still in place to keep them attached to the rail.

[joncunanan]

I'll give that a shot hopefully this weekend. It's hard for me to work on it during the week. Thanks for the advice! I'll post an update with what happens.

[joncunanan]

so I took the upper intake off and pulled fuel rail out. I bought a circuit tester light to check for power. I took off each injector off the rail expect fuel to leak out but it was dry. I tested all 4 leads and they all have continuity.

the fuel hose for the return line was the one leaking from the clamp so fuel was at the rail. i tried cranking without the injectors on to see if fuel would come out the 4 holes out of the rail but nothing came out. I am so confused. if there was fuel in the return hose, is it safe to assume the pump gets gas to the feed line through the rail and back to return line?

I checked again under the car and the hose that connects to the back of the fuel filter up through a hole in the chassis then what looks to clamp to a hard line near the top of the tank is leaking. there is foam around that clamp and it's damp and soggy. do I need to drop the tank to replace this hose?

I am so lost. can this leaking fuel hose be the cause of all the fuel supply issue at the rail and with the injectors?

[richardodn]

So if you pulled the injectors off the rail and no fuel came out, it's definitely a fuel supply issue. As a side note, all the injectors should have power in start and run. Control is provided by grounding through the ECU in 2 banks; 1-3 & 2-4. So if you have no fuel to the rail, what's the likelihood you installed the engine with the supply and return lines reversed? That would explain a dry rail and leaks suddenly appearing.

[joncunanan]

thanks for the advice guys. i got some free time while the kids were away. i unhooked the fuel lines and reversed them back. there was a little bit of pressure in the lines so i tried to keep a rag there from preventing it getting everywhere, but there was still some light splashing. i wiped off as much as i could then let it dry for a few hours.

i plugged the battery back then tried to start. it turned over but still didnt catch. i did the stomp code again and the 1216 tps sensor was cleared now, but now i got a 1252 which i researched is fuel injector #2 issue. one of the threads said it was due to no current/voltage going to that injector, but i tested it with the light tester and it was fine. does it mean the injector itself is bad or clogged? is this enough to prevent the car to start?

[joncunanan]

some busy weekends lately but got a chance to try and put water bottles under the fuel injectors and try to crank and see what happens. i tried cranking it for a bit and it didn't spray a lot of fuel out. i tried cranking again, then took out the water bottles and its like a few droplets. i put a dry rag and laid it like a blanket under all 4 injectors and cranked again and it's faint discoloration from fuel. like its not spraying, more like trickling? i still get code 1252 doing the stomp test.

does this mean my injectors are bad? the condition is unknown, i mean when i pulled them out almost 2 years ago when it still was running, then cleaned them before i put them back. could code 1252 mean a bad injector or is it like the wiring for the pulse trigger bad?