This is a cold start issue, I could take a video, but it'd be pretty boring.
I've got a 1990 I'm flipping. Only major issue is that it cranks for 10-15 seconds when cold with a bunch of throttle feathering to make it start. After it's warm (5-10 minutes of idling), it'll spring to life with less than a second of cranking.
compression is 165-175 on all four, stock everything, brand new timing, verified a million times, set to 11 degrees. It's done it with two different coil packs, two different sets of NGK blue plug wires. It does have irridium plugs from the PO, those will be swapped for stock NGKs soon, but I doubt its the problem, read below.
When I jump the fuel pump in the diagnostic box, it doesn't seem to help. However, when I clamp the return line with some vice grips, it dramatically helps reduce the cranking time down to 3-5 seconds. I'm guessing something in the fueling department.
So what's the thought, fuel filter, regulator, or pump? Thanks.
Stock ECU? Can you swap in a known good one for a test (do you still have the one from your smurf?). I'm pretty sure the ECU performs the "choke" function by adding injector PW just like our MS's.
Not sure how the ECU could fail to cause this but otherwise still control the car OK. Maybe it's missing an input needed to determine that it should choke. Air temp sensor is in the AFM and water temp sensor on back of head. Perhaps verify those at the ECU plug with a multimeter.
yeah, it's just a little extra air, I'm not flooring it. And I'm not 100% sure that's even helping at all. With my experience with 4 carb motorcycles, it's always helpful to simultaneously floor it and crank the starter.
I'm assuming this is all poor cold start enrichment issues. Either part of the fuel system is on it's way out, and clamping the return line helps give it a few more psi, or one of the temperature sensors is on the way out and it thinks it's warmer than it is. That would give it less fuel, and again clamping the return line gives it the extra fuel it needs.
The AFM has not been opened in it's life, but again, it's from a different '90.
Josh, is there any way someone could look through the AFM while you're cranking to verify it is actually moving?
Also, I'm sure it wouldn't hurt to check the pot the flapper is connected to with a multimeter to see if the 23 year old contacts are still good - especially in the first 25% of its range.
(Think of it as a bad TPS that is worn in the range it works in 90 per cent of the time)
I've verified the flapper is moving. I can plug in a spare AFM (which has been messed with) to double check though.
So I did end up taking some videos for y'all. Both were taken without touching the gas pedal.
Return line clamped:
And I get this:
If I IMMEDIATELY remove the vice grips, this is what I get:
Also, I checked my coolant sensor at the ECU.
This is taken a few seconds after start up.
And once warm (really warm):
As you can see it's dead on for the FSM's 2.5v cold and .4v warm range.
I also got a hold of the previous owner and he said the fuel filter was replaced when he bought it three years ago. Once I get a fuel pressure gauge I'm checking the pressure, all signs are pointing towards the pump if you ask me.
I'll try another ECU next. I'm bringing it to a friends to get rid of the horrible Delrin motor mount. I'll see if I have time to try a different AFM before then as well, however the current one was working wonderfully in another car. The same car I'll be trying the ECU from in fact.
Interestingly enough, my issues are with a '90 AFM and I believe a '93 ECU.
'90 AFM and '90 ECU test will happen Friday.
Is the consensus that a bad fuel pump would be giving me hesitation issues in the rest of the range as well?