Have Spark, Have Fuel, Have Compression, Have Air - No Start

[AWDBOB]

Hey R3V-

I am helping a buddy get his car back on the road after it was sitting for 10 years. Car cracked a head, and was parked for 10yrs.

Backstory:

The car is a 1990 325i, automatic. My buddy had some extra time during covid and wanted to get his E30 back on the road, so he followed an E30 guide, had a crack free 885 head refinished, and performed the HG job. After that, the car would crank but wouldn't start. Wouldn't start with starting fluid, had spark and fuel, but wouldn't fire. I helped him a few days, we swapped every part imaginable with known working parts from my car.

Fast forward:

His business picked back up and brought the car to my place to finish up and get running. First thing I did was check compression, and it wasn't building any. I pulled the head off and brought it to my old trusty machinist, and he found that whoever did the head locally put the seats in crooked and had no valve seal. COOL, explains the no compression.

I got the refinished head on, and before buttoning the car all of the way up, I had everything but the cooling system hooked up, and started it. Car fired right up after building fuel pressure. COOL, problem solved.

With confidence, I then installed the cooling system, accessories, belts, etc etc.

Go to fire the car up, no dice. Same situation as before. Has spark, has fuel (plugs are soaked), verified compression on all cylinders. Verified timing, no issues there. Same exact scenario as before I did all of the work, but this time, with compression.

Plugs are getting soaked, so I figured I'd swap the coolant temp sensor assuming it's telling the DME car is cold so sending too much fuel and washing the cylinders. No dice. Pulled each plug to verify a strong spark. I had a battery with a dead cell once, too, so I also swapped over a fresh battery from Linda. No dice.

Other odd bit of info: if I unplug/replug the battery the first turnover of the engine it tries to come to life but doesn't, and goes right back into it's crankycrankcrank mood.

I have since swapped with parts from my running car:

-Injectors (2 sets, one m50, one m20b25)
-DME
-Crank sensor (ohm at 500)
-Coolant temp sensor
-Plugs
-Coil
-C191 (injector harness)

The car, when started the first time had the AFM unplugged. I have reinacted that scenario, with no change. I unplugged the blue coolant temp sensor plug, and the car sounded like it was firing moreso than normal, just not enough to get it going.

The car started, I shut it off. Installed accessories, cooling system, belts, and now she just cranks with spark fuel compression and air, and won't start.

I am at wits end, and am turning to the R3V crowd for advice. I have NEVER been stumped like this before, and it is incredibly frustrating.

[AWDBOB]

The only thing I can think of that I haven’t messed with is a clogged fuel return line, which I assume would provide similar symptoms to what I am experiencing.

[mjweimer]

Probably time to check the fuel supply pressure. Do you have a gauge and a T-fitting that could assembled in-line with the supply?

If the return line was clogged I would expect it would still try to run but not well. Easy enough to check by pulling the return line off the regulator and blowing through to the tank. Absent of a gauge, you can also pinch off the return line a bit to raise the line pressure and see if it helps.

Shout at me if you want to discuss further.



MJ

[roguetoaster]

Have you checked that the crank damper hasn't sneakily separated and clocked over?

[AWDBOB]

Probably time to check the fuel supply pressure. Do you have a gauge and a T-fitting that could assembled in-line with the supply?

If the return line was clogged I would expect it would still try to run but not well. Easy enough to check by pulling the return line off the regulator and blowing through to the tank. Absent of a gauge, you can also pinch off the return line a bit to raise the line pressure and see if it helps.

Shout at me if you want to discuss further.

MJ

I was planning on getting an exact pressure reading today. Outside of visual and stethoscope, I have not put my tester inline yet. An odd tidbit as well is that starting fluid does not help the case any, despite the car having strong spark. Which leads me to believe that the fuel is washing the cylinders upon cranking. I've let the plugs sit out overnight, I will pull the fuel pump fuse and try starting fluid before putting any fuel through the car today.

Have you checked that the crank damper hasn't sneakily separated and clocked over?

I did, I pulled it off and made sure the key was present, however, I did not pull the crank bolt/cog to check if the woodruff key is present- so good call there! I'll verify that today.

[AWDBOB]

Things to note:

1) After letting it sit overnight with the plugs out it started right up with fuel pump fuse pulled, running on starting fluid only.

2) Fuel return line in tank completely clogged, line from rail to tank is clear.

3) I pumped out all of the fuel in the tank in case of old fuel because I now know it's rusty in there (the car's owner did this as well before the car came to me). Filled with fresh gas, took off return line and let return drain into bucket. Hooked all lines back up correctly, installed fresh plugs. Still, immediately floods engine, dumping fuel into cylinders and not firing, even with the assistance of starting fluid. No fire, plugs soaked after a few cranks, with return line removed and draining into bucket.

3.5) Found out I don't have a fuel pressure gauge so I haven't pulled pressure yet, but have also tried different FPRs all off of running cars, none of which made a difference.

[ADEN]

What injectors the car has????
mine is the m52b25 and is flooding my enging when o2 sensor faulty

[misterTT]

Did you ever solve this? I'm going through basically the same exact series of problems; in my case, I do have the correct fuel pressure, new FPR, etc... and still getting what seems like immediate flooding anytime I crank it over, but it starts up fine (for a second or two) with starter fluid - so there is spark.

[AWDBOB]

Did you ever solve this? I'm going through basically the same exact series of problems; in my case, I do have the correct fuel pressure, new FPR, etc... and still getting what seems like immediate flooding anytime I crank it over, but it starts up fine (for a second or two) with starter fluid - so there is spark.

Yep-

When I put the rebuilt-rebuilt head on, I verified compression on the cylinders that were low before and had compression now, and stopped there.

What I should’ve done was check all six, but I didn’t.

After all of that testing and swapping of parts, I checked compression on the cylinders I didn’t check initially and they were low, to the tune of like 50psi, and fuel won’t ignite under 70ish from what I’ve seen.

So I’m assuming it started the first fire up (and then if I let it sit overnight, on starting fluid), before the fuel could wash the rings on those cylinders low in compression.

He bought a SETA shortblock from me and I installed that under the rebuilt head and all was well.