I've checked everything, what's left?, My car is downright REFUSING to run Options

[JDW914]

Okay, so a bit of background.

Late last year, my car ('74 2.0 with Mark De Bernardi's 2056 hardware kit) suffered a betrayal from one of the old Bosch injectors, resulting in a fire which, while happily small and caught quickly, ruined the engine wiring looms, MPS, and battery. I figured repairs would be pretty straightforward - and they were. Got parts frome eBay, and new looms from Jeff Bowlsby, took the car to the shop of the painter who did the original restoration bodywork on it, and dropped, cleaned, and rewired the engine while he fixed the decklid and rollbar up. Threw the engine back in, got it running, tuned it to perfection, and went to reassemble the car.

Now this is the point where everything started going very wrong. We put the decklid in place and went to install the trunklid, and the trunk hinges both sheared at the bolt. I replaced the bolts, and we noticed the sheet metal flex mounts for the hinges were both nearly undone at the welds as well, so the painter offered to weld them up, which I agreed to. We disconnected the battery just in case, welded them up, and assembled the car. I got in to drive it away, and the car would not start. Engine turns over, kicks into life, then dies.

And this is all I've gotten it to do since, and I am out of ideas. EVERYTHING checks out and is working, to the point where I'm not sure how it's physically possible that this thing isn't running.

So far, I have verified:

- There is good fuel pressure (32-33psi at prime, 33-35psi during cranking and running)
- All 4 injectors (matching, new SMP FJ6 units) are firing
- There is spark, and it is timed correctly
- The point dwell is optimal (about 47 degrees)
- There is strong compression (around 140-155# in all cylinders)
- The valves are all actuating, and have correct lash
- All electrical and pneumatic connections are secure

And I have tried:

- Draining the tank and using fresh fuel (what was in it was several months old)
- Swapping coils from the stock-alike to an MFD Blaster 2 with appropriate ballast in case the coil was failing to charge up at running speeds
- Swapping the ECU out between a NOS replacement and the original which seems to be free of damage
- Setting fuel pressure all the way up and all the way down as far as the Bosch regulator allows
- Clamping off the cold-start injector
- Starting the engine while hooked up to a battery charger
- Unplugging the TPS

Not a thing so far has produced the slightest change of behavior. The closest I've gotten to having it run is, with WOT, holding the starter keeps the engine "running" at about 800rpm, with constant combustion, but no pickup of rpms or power, which is still pushing me towards either spark or fuel mixture.

What has me completely aghast, though, is that this thing was running perfectly and not a thing has changed. I'm beginning to think it's just angry at me.

What the heck am I missing?

[Root_Werks]

It sounds like you're not getting past the cold start cycle.

[914_teener]

So did you get a new MPS and calibrate after the old one burned and was destroyed or did we miss something.

[JeffBowlsby]

I usually dont jopi nthese discussoin, but here goes:

1. What MPS part number do you have and does it hold steady vacuum?
2. Known good original MPS or recent rebuild?
3. Fuel pressure is too high, should be about 28-30psi if I recall correctly. Check the factory specs.
4. Trigger points verified to function?
5. Fuel injector grounds connected to ground?

[JDW914]

Yes - I should have specified better - I did replace the MPS. The old one was pretty much destroyed.

The new one is a -043 P/N that has been re-manufactured by Rich Bontempi. It holds vacuum and the impedance is in the right area.

The fuel pressure is boosted to match the more aggressive cam and slightly increased displacement (although I based my calculations on a 32psi stock spec and the Bosch injectors). I'll redo the calculations for the new injectors and readjust it more precisely when the thing runs again.

Trigger points are working, as the injectors are pulsing (I've squirted fuel into a jar out of all 4 with the engine cranking). Is there a good way to tell if they're consistent? It's crossed my mind that they might be intermittent or sticky.

The injectors ground to the stud at the back at the back of the block, right? I'll double check continuity when I get a chance to be sure of them, but that ground is secure.

[914_teener]

I usually dont jopi nthese discussoin, but here goes:

1. What MPS part number do you have and does it hold steady vacuum?
2. Known good original MPS or recent rebuild?
3. Fuel pressure is too high, should be about 28-30psi if I recall correctly. Check the factory specs.
4. Trigger points verified to function?
5. Fuel injector grounds connected to ground?

I.ll just go there:

Story isn.t plausible given the name dropping going on....big qualifier.........



IMHO.

[rjames]

MPS needs to be calibrated to your engine.

[JDW914]

I usually dont jopi nthese discussoin, but here goes:

1. What MPS part number do you have and does it hold steady vacuum?
2. Known good original MPS or recent rebuild?
3. Fuel pressure is too high, should be about 28-30psi if I recall correctly. Check the factory specs.
4. Trigger points verified to function?
5. Fuel injector grounds connected to ground?

I.ll just go there:

Story isn.t plausible given the name dropping going on....big qualifier.........



IMHO.

Don't know what to say to that.

I'm name dropping because A. those are the people I got the parts from and B. I'm fairly certain that the new components are good, and wanted to communicate that these aren't random junk parts or shoddy replicas.

Honestly, the situation the car is in seems basically impossible to me. It was JUST working. I'm basically hoping somebody will come along and point out something stupid simple that I've missed.

MPS needs to be calibrated to your engine.

This is new to me. I know that there are several available adjustments, but I was under the impression that messing with any of it "should be a LAST RESORT process" and "you'll usually be better off if you get a rebuilt unit and send in yours as a core."

How would I go about it?

[iankarr]

Cylinder head temp sensor?

[second wind]

My car was down for three months and I "thought" I had spark. Under compression spark plugs do funny things. Replaced the coil and car has run fantastic ever since. Just an idea.
All the best,
gg

[porschetub]

why up the fuel pressure for a big cam …..never heard of that but my skills are with later systems but still don't see it working.

[falcor75]

"Not a thing so far has produced the slightest change of behavior. The closest I've gotten to having it run is, with WOT, holding the starter keeps the engine "running" at about 800rpm, with constant combustion, but no pickup of rpms or power, which is still pushing me towards either spark or fuel mixture."

I guess this is with the key in the "engine start" position, does it die when you release the key? I would try taking the ignition lock ou of the equation, bridge the fuel pump to run on the relay board and then just use a remote starter switch directly on the starter motor.

Gearbox earth strap in place?

[BeatNavy]

Cylinder head temp sensor?

Given everything else you've described, this would be one of my prime suspects -- the CHT.

I think you're on the right track with fuel mixture, and if the CHT is bad or the circuit broken it may initially attempt to start but will quickly flood and not do anything after that until the fuel evaporates. Then you can try again, and the cycle repeats. Does this sort of describe the behavior?

If you pull the plugs after attempting to start, are they wet? Easy enough to check.

Situations like this you definitely need to go back to rock solid fundamentals of spark, fuel, compression, timing and verify them 100%.

[JDW914]

The CHT is a good call. I will check it out and make sure it's got the right resistance.

I'll also check the plugs for signs of rich/lean running.

I don't think it's ignition switch related as the engine does run with the key released, just only for a few seconds. It actually starts and catches quite quickly.

[914_teener]

Cylinder head temp sensor?

Given everything else you've described, this would be one of my prime suspects -- the CHT.

I think you're on the right track with fuel mixture, and if the CHT is bad or the circuit broken it may initially attempt to start but will quickly flood and not do anything after that until the fuel evaporates. Then you can try again, and the cycle repeats. Does this sort of describe the behavior?

If you pull the plugs after attempting to start, are they wet? Easy enough to check.

Situations like this you definitely need to go back to rock solid fundamentals of spark, fuel, compression, timing and verify them 100%.

Without a ground to the CHT.....the engine will not run....period.

So.......the OP states ......everything was fine until he had an engine fire burning up harnesses.

That.s nothing trivial.

He should begin by ringing out any circuit connected to rhose harnesses to prove them out to eliminate each possiblity.

Again not a trivial task and without a systematiic approach instead of wishful or magical thinking a solution will be slow in coming.

[GregAmy]

Data point: my intermittent start, start then dies, random dies.

http://www.914world.com/bbs2/index.php?sho...=291477&hl=

Spoiler alert: bad MPS diaphragm. It held vacuum.

[rjames]

This is new to me. I know that there are several available adjustments, but I was under the impression that messing with any of it "should be a LAST RESORT process" and "you'll usually be better off if you get a rebuilt unit and send in yours as a core."

If the diaphragm is toast the car may not run. If you replaced your original mps it is likely that it will need to be tuned to your engine, even if it was recalibrated to factory specs.

To adjust it you’ll need to be able to get to the adjustment screws (do a search- lots of threads on adjusting the MPS) and have access to a wideband AFR meter.

[914sgofast2]

Guys, You can’t set the MPS if the motor won’t run!
I suggest checking to make certain the engine/trans are securely grounded. Check for presence and cleanliness of the ground strap between the rear of the trans and body. Because the car was repainted due to the engine fire, also check (1) battery negative cable connection to body is sparkling clean; (2) all the wires going to the grounding point behind terminal/relay board in left (driver) side of engine compartment are clean and paint free.

[SirAndy]

Cylinder head temp sensor?

(IMG:style_emoticons/default/agree.gif)

[Olympic 914]

The CHT should read somewhere around 2500 Ohm resistance cold and then go down to below 100 when hot.

You could trick the ECU by substituting a 2500 Ohm resistor between the lead where the cht plugs in and ground. That would mimic a cold situation to the ECU. it should work to at least start the engine. But if left in place it would be too rich to drive around after warmed up.