Cold Start Issue 914-4, Admitting I'm stuck and asking for help Options

[Blue Lightning]

Car: 1976 2.0, FI

Background: bought in November last year. I am least the 4th owner. Drove a couple times, then plugged up the fuel filter (? no fuel pressure when the fuel pump was running, but see note below on replacing the fuel pressure regulator), so spent a couple months with the gas tank out and replacing the fuel lines, pump (and yes, filter). Read a lot in the meantime, so corrected vacuum line issues (vac advance was connected, replaced all the lines that didn't already look new, added hose clamps). But where the car started and ran well last year, I can't get it to happily start any longer. While cranking, it will skip and catch. After a few minutes of cranking (and skipping and catching) it will finally start and run fine for a few minutes but only idle around 1000 rpm (until the AAR warms up the rest of the way?), then dies. Starter fluid has no effect, so guessing it is running rich? Pulling the air hose off the cold start injector while running causes the idle to increase to maybe 1400 rpm (but with hunting, as you might expect with that big leak). There are a lot of threads on what to look for when the engine is running lean, but few on it running rich.

Some things I have checked:
- AAR works (https://youtu.be/YmO1ZCLDB7g)
- Compression is good (130-140 psi cold)
- Replaced the MPS last weekend with new one from autoatlanta, after finding the previous one would not hold a vacuum
- Replaced fuel pressure regulator after finding it bad (yes, I've been told these never go bad, but this one would not hold any pressure). Fuel pressure set to ~29 psi.
- Timing is good (~27 degrees at 3500 rpm with vac retard disconnected)
- Vac retard mechanism is working (checked with vacuum pump)
- Spark on all 4 cylinders (checked by timing light)
- Smoke tested the intake...only leaks now are the bearings on the throttle plate
- CHT reads 2k at cold, ~250ohms at warm/hot (at splice connector)
- Plugs look okay (see attached)
- Fuel injectors are all spitting fuel (checked into bottles...all about the same) and have new seals
- idle adjust screw has some control, but I cannot get the idle above 1000 rpm with it
- valves adjusted back in December (my first time, but the car runs so I assume I didn't do too bad of a job?)

I'm at a loss of what to try next. (IMG:style_emoticons/default/hissyfit.gif) I'd like to consider myself fairly good with cars (we have a 1966 Mustang, as well as a Mazda RX-8 that I have kept running for >20 years), but I'm about ready to throw in the towel and have the 914 towed to someone smarter than me!

Thoughts?

[Blue Lightning]

Got it - agree; set aside cooling issues for the moment as not likely related to the cold start issue.

What I’m trying to get a sense of is whether there is some underlying fast overheating (ie mouse house in the tin) that would quickly confuse the Fuel Injection by maybe starting too rich but very quickly going too lean to re-start if the 3/4 side head when the CHT is overheating.

I have not seen any indication of debris that I would expect a mouse house to leave on the floor under the car.

I did find (what I consider) a decent set of videos on debugging a won't-start-914:

https://youtu.be/-bMBoADt7Fg?si=wxh7gFKWUtGtuKN8
https://youtu.be/MSQWQ2Nd2Ck?si=ATNib8WZ99NExASH
https://youtu.be/fbmanDTIun8?si=ukzTAFeUDxrAAm5_

I mention this as when going through their ECU connection debug in January, I noted that the CHT was reading 4.95 kOhm at the ECU, where it reads ~2 kOhm at the splice today. At the time this didn't seem unreasonable given the data at http://www.914world.com/bbs2/index.php?sho...351065&st=0

but the Kjell Nelin article linked above brought me back to those videos where I saw the resistance measurement I made at that time. Not sure if I buggered that measurement, but want to go back and double-check it. In the video series, the root problem ended up being a disconnected CHT, so it might be a wiring problem making the CHT look (close to) open at the ECU that is preventing the car from starting. Hopefully nothing wrong with the wiring harness (IMG:style_emoticons/default/smile.gif)

I did order a new CHT. The current plan of attack is:

- Check CHT value at ECU (while wiggling wire, etc.)
- Replace CHT with new, if necessary (I have one Brad Mayeur's spacer/standoffs on order, too, so would like to add this if I pull the CHT, which I probably will anyway since I bought a new one)
- while ECU is disconnected, verify the coil resistances of new MPS at the ECU
- probably check all the leads at the ECU connector, since I have disturbed quite a bit of stuff over the last few months
- Crank engine for a minute or so, but pull spark plug(s) before it starts running and check for gas/wet
- Remove fuel line going to cold-start injector and plug, to verify this isn't flooding the manifold
- Disconnect and plug decell valve hoses (this was suggested in the Kjell Nelin article)