Exhaust valve replacement - now no start!

#1

'89 325is. >300K miles (est), semi-daily driver.
Had the car about 6 years.

Cylinder 5 exhaust valve ended up getting some carbon deposit build up on the valve land and lost compression (62 psi compression). Drove it into the driveway on 5 cylinders (ran really good, all things considered). Removed the head and everything attached to it as necessary. Cylinder walls are super clean. Pistons looked really good. I pulled a replacement valve from a donor head that had a damaged distributor boss, lapped it in, and reassembled with all new gaskets & seals.

Compression on all 6 is between 120 & 125 psi
I have verified that I have spark on all 6.
Timing was set crank to block notch, then verified on harmonic balancer after a couple revolutions. Checked again via TDC on balancer with valve cover off and by wiggling the cyl #1 rockers to verify they’re off the cam.
I am getting fuel from the injectors, though I have yet to pull the rail.
I have spark via brand new plugs gapped to 30.
CPS and Cam Sensor resistance read within specs. CPS was untouched throughout this process. Plug wires are correctly connected at distributor (I’ve re-checked a thousand times).

Will NOT start. Will not even try to start. When I’m turning it over, it periodically slows the starter and/or hisses into the intake as if it’s trying to start backward. I’ve tried spraying starting fluid into the tube just downstream of the ICV, and it definitely puffs back into the intake, making the throttle body snorkel briefly expand a little. When I give up trying to start it, the intake manifold will even feel slightly warm, and the exhaust will feel stone cold.

I’ve run out of things to check. The regular boards are clueless. Hoping the more hands-on racing community can help. I suspect I’m missing something obvious. Please advise!

#2

I had this symptom once. It turned out that the distributor rotor didn’t go back on perfectly straight. As a result it was off-axis and not striking most of the conductive elements on the dist cap. It was totally invisible until one removed the dist cap and looked closely at the wear pattern on those conductive elements.

If you are indeed getting enough fuel pressure, then your CPS is ok. It’s not enough to just be getting fuel, your low pressure pump could do that. You can get a fuel pressure gauge at harbor freight for beer money. Also, reseat your injector harness connector.

Need to pull each plug wire and see that it’s sparking. Might want to try a different coil.

Make sure you’ve not neglected to connect something to the throttle body. A big vac leak would fit the symptoms.

Check your engine ground on the left side of the oil pan.

Reseat your DME connector.

Just because there are other things that you’ve not screwed with, doesn’t eliminate them as possibilities. Weird shit happens.

Might want to pull the injector harness and see that they are actually spraying.

#3

Holy cow, thanks for the quick response, Ranger! Will be looking into each of your suggestions.

A couple questions:
Were you getting spark when the rotor was not on straight?

If I shoot the intake manifold full of starting fluid, doesn’t that preclude the fuel pressure? Wouldn’t it at least try to start?

Will certainly review vacuum leaks - I’ll never live it down if that’s the issue.

DME connector… huh, ok, will re-seat.

Ground strap was replaced as part of this effort. The old one was getting rough. Got good ground to chassis.

Will go through fuel system as well… not looking forward to pulling the rail.

I appreciate your thoughts on this - your single answer outdoes anything I’ve gotten from any other source.

#4

The symptoms would tend to indicate a problem with cam timing or spark. Your checks of cam timing would seem to eliminate that as a possibility. That leaves spark as the most likely suspect. As Ranger pointed out it is possible to incorrectly install the rotor and that would be the first thing I’d check. I would not hurt to have another pair of eyes verify correct plug wiring.

#5

[quote=“Bxb8879” post=82999]Holy cow, thanks for the quick response, Ranger! Will be looking into each of your suggestions.

A couple questions:
Were you getting spark when the rotor was not on straight?

If I shoot the intake manifold full of starting fluid, doesn’t that preclude the fuel pressure? Wouldn’t it at least try to start?

Will certainly review vacuum leaks - I’ll never live it down if that’s the issue.

DME connector… huh, ok, will re-seat.

Ground strap was replaced as part of this effort. The old one was getting rough. Got good ground to chassis.

Will go through fuel system as well… not looking forward to pulling the rail.

I appreciate your thoughts on this - your single answer outdoes anything I’ve gotten from any other source.[/quote]

Re. spark. Sorry, I just don’t remember. I might have tested the one or two plugs that were sparking.

Re. starter fluid. I’ve never had much luck with that.

Re. vac leaks. They are diabolical.

Re. injectors firing. Harbor Freight sells a kit sort of thing that can tell you if your injectors are getting a “fire” signal. IT’s called a “noid light”, or something like that. It’s a weird name. They fire in banks…1-3-5 and 2–4-6, which, frankly, amazes me. I mean, how can that possible work? But Bosch has been doing this for a while so somehow it must work.

#6

Even with a pretty large intake leak, a healthy dose of starting fluid should allow the engine to fire and run briefly if cam and spark timing are correct.