Agree with this.
You can see the belt is running much deeper in the V compared to the marks that are on the pulleys. I wonder if the nut has loosened itself...

Have you checked battery voltage and alternator output?

Sounds so much like a vacuum leak.
I agree with the post that recommends removing the belt and starting the engine.

I am just thinking out loud and still think the AFR looks whacked, etc, - but wondering if the alternator is not charging - is it possible the battery voltage dropped low enough to cause unreliable spark/back fires, mess with wide band sensor function, and not have enough juice to allow engine revs?

Just another aspect to consider after seeing the apparent misconfiguration of the alternator belt pulley?

Do you have a datalog for the engine running in this condition?

+1 swap out battery or test, easy cheap stuff first.

If you have the CIS airbox, with a flapper valve in it....check the flapper valve. A backfire can cause the valve to come loose and not seal properly....resulting a big air leak, rough running or no-start condition. This may very well also show up as lean AFRs, due to the leak.

regards,
al

I have no reason to suspect charging issues, or at least an actual lack of charging. When it’s a no-start, car will crank and crank as long as I have the key turned, everything powers up normally. That’s not to entirely exclude possible alternator issues. I will re-set belt tension when I get home - belt was replaced in June of last year when I had a shop take care of a few things I didn’t have time for before a trip.

As I learn more about the condition in bits and pieces (I’ve been talking about it with a friend, too) I’m inclined to think the problem is either a sensor-output problem (the Megasquirt isn’t seeing somehting that it’s expecting) or a vacuum problem or both. Will check signal from crank position sensor when I’m home (it’s got a Goingsuperfast 36-1 toothed wheel with a CPS from I don’t remember what). Unfortunately I haven’t been able to do any data logging. I think this is due to a firmware mismatch - I’ve been talking to DIY Autotune about it and will get that sorted out when I get home and get some data.

I don’t have the CIS air box but the remnant of the base with the flapper valve in it is still there. Seal on the valve looks good as far as I can tell. Certainly nothing *obviously*wrong with it.

How did you check the vacuum hose? An easy way to check for vacuum leaks is to spray carb cleaner on every component. If the tone of the engine changes, the engine is sucking in the cleaner through the leak. I think it's very difficult to visually see vacuum leaks on an engine. If the engine sucks cleaner through the actual intake air cleaner the engine note will change.

I just verified that it was connected and attached. I can’t imagine that such a small vacuum leak from a FPR vacuum hose that had a leak would cause such a large problem. Will defo test everything with carb cleaner when I’m home.

Thanks for all the input on this. Got back from vacation last night and will have time later this week to work on the car, and followup then.

Have not had a lot of time for diagnosing this since mid-October, and then I wasn’t very productive with the time I did have. And then I spent a week dealing with stupid battery issues after I drained the battery from all the cranking during testing, recharged it, accidentally left ignition one when I went in for the night one night, couldn’t recharge battery using trickle charger, got it charged at FLAPS, blah blah blah and then it’s cold as balls and I can’t work in the garage, etc. etc.

but I came up with a plan of attack and finally today I was able to corral my SO for a little bit and had her crank it for me with the throttle open while I sprayed carb cleaner down the intake and it would run on that. So it’s getting spark and it’s not getting fuel. Fuel pressure gauge on engine reads 8psi - I don’t remember what it is set at without looking it up, but it sure as hell isn’t that and it wasn’t that low when it was running badly in October. But obviously it’s not getting fuel. So next to check the FPR, filter and pump.

Should be around 32-35 psi running IIRC for 30 lb injectors.
8 psi isn’t going to cut it for EFI.
If you haven’t touched the FPR, a good CIS pump should run at whatever it was originally adjusted to.

Yeah, that sounds about right. I've got what it was set at in my records somewhere, in addition to what the injectors came off of. Though (@timmy2) the car is running on a Megasquirt, so no CIS pump.

You may well still have the CIS pump. I re-used mine for conversion to ITB EFI. It should be putting out over 50 psi unregulated, and the pressure regulator should control that to about 43 psi (that's what I run). Anyway, it sounds like you found at least one of the problems. Keep us posted.

Phil G.

I have been running Megasquirt for 10 years on Bitz kit.
I kept my CIS pump as well. The FPR regulates the pressure down.
Running around 37 psi now on my new ITB system.

The need to replace the FP isn’t needed for EFI. As opposed to carbs.

Ah, yes, you're right. I don't remember what pump is on there so I'll go look through the PO's records. I'll have some more time to work on the car tonight. It's warm for a bit this week, which helps.

Put a gallon of gas on it because tank was near empty and why not (it would be tragically hilarious if that were the problem) but no change, to little surprise.

Fuel pressure gauge reading around 35psi, so normal - not sure why it was ~8psi last week (it was normal earlier when it died). It would fire once or twice when I cranked it, though. Then just for curiosity’s sake I pulled the vacuum line off the FPR and it starts and runs, idling at about 600rpm. That’s interesting. Off to plug the laptop in.

Maybe the FPR has gone wonky.
I’m assuming Non running just on fuel pump it is 35 psi, regulating way down when it sees vacuum when running?

FP gauge reads around 35psi when the FPR sees vacuum, 40psi when I unplug it. Which says that it isn’t *not* working at all.

I’ve had an intermittent high idle issue that appeared a year and a bit ago - it most often idles around 1800-2000, though not always. When I unplug vacuum line from FPR, idle goes down to ~900, which is basically normal for cold idle. (Unplugging IAC does nothing in either case.) So this is also getting me some progress in figuring out my fast idle, which I assumed was an air leak. MAP at ~2000rpm is around 40kPA, so not suggestive of a big air leak. Perhaps also the FPR.

I can’t exlude that it was simply….out of gas? I added gas and cranked it for 5-7 seconds three times, and it caught once each time but it didn’t turn over. But perhaps it was out of gas and I just didn’t give it enough time to get fuel in the system. Gauge was empty but not on the warning light, and gauge has been reliable in all the years I’ve had the car. It doesn’t make any sense that removing vacuum from FPR would let car instantly start and behave normally. And I’ve run cars out of fuel before (durrrr….) and they all die the same way. Car didn’t die this way but I may just be parsing too fine of a difference. But I am suspicious of the FPR and may load the parts cannon with one.

If somehow I just ran it out of gas, feel free to make fun of me forever.