4.0 OHV Persistent Hard Start. Looking for ideas

[Kirby N.]

Hey all! I am having a persistent problem with my ranger. I have tried a lot of stuff- and I am still loosing, so I thought I would ask for some help.
Its a 1991 4.0 OHV Ranger. Manual Tranny Manual T Case.

The symptoms:

It starts really hard almost all the time. It has gotten worse, and more often. Originally it would start sometimes hard, I thought maybe it had something to do with the ambient temperature. It will not start without some throttle input. Initially it sounds like it is going to start, then it goes into this long crank no start. If I open the throttle in that crank just right it will fire and start.

It also idles a little odd. Like rough. when it is at 750 rpm it vibrates more than I think it should, makes a loping sort of sound and the throwout bearing makes a clatter.

What does it have done:

Its a ford remained 2000 block. It has 1995 (95tm) heads that I had rebuilt using parts from new old stock 93tm heads that were incompatible, but the valves and springs were the same. I had them decked and checked for cracks and valves lapped. Everything engine wise is stock, but I replaced what I could while I was there.

When I had the engine out, I replaced everything I could possibly replace with new old stock parts if possible.

It got some "remanufactured and flow matched" 5 hole injectors when I put it together with new o rings.

It has never really idled great, but it did start well before the last few months when it started starting hard intermittently. It now starts hard consistently.

No check engine light, no codes

What have I done to trouble shoot (always resetting the computer when things change):
- I did a smoke test. Found one leak on a hose clamp on the intake tube. Tightened it up and and that was it.
- I replaced the fuel pump. I had a new spare one. I checked the fuel pressure and it was in spec, but I decided I wanted to be sure.
- I have replaced every sensor I can think of: TPS (new old stock ford unit, used junk yard unit), Crankshaft Position Sensor twice (2 new old stock ford units), IAC (new old stock ford unit, used junkyard unit), MAF (used Junk Yard Unit), replaced the purge solenoid (new old stock ford unit), replaced the coil (new old stock ford unit), replaced the intake air charge sensor (new old stock unit), Replaced both coolant sensors (new old stock units), replaced the throttle body (new Old stock ford unit)
- I tried a used Junk Yard ECU from a 1993 manual explorer. It showed a CEL, but didn't change the starting condition.
- I tried a used loaned from a friend ICM. No change. Made sure it was mounted and grounded no change.
- I tried all new copper spark plugs. No change.
- I checked spark on all cylinders by unplugging from the coil. All have spark. I checked spark on cylinder number 4 when cranking. It has spark.
- Checked the grounds, all seem good.
- verified that the spark plug wires are plugged into the correct plug for the firing order.
- Verified that each injector is "clicking" consistently when running.

I am kind of out of ideas. I dont really know what else to check or try. I am considering ordering a new wiring harness because that is all I can think of that is left. I went over the engine harness when the engine was out and did some re taping and cleaning. I also had an issue with the wiring harness near the fuel pump from a careless frame drill I did, but I repaired it. no wiggling makes a difference.

It doesn't change anything if I cycle the key when I start it.

If I resart it immediately, it starts ok with no throttle input. If I wait 1 minute or more to start it, it starts like crap again. like it will initially sound like it is going to start, but then will just go in to this long crank no start. If I dont touch the throttle it will never start. If I open and close the throttle in and out, it will eventually start.

I am really at a loss for what to do. I was hoping you guys would have some ideas.

I am thinking maybe injectors? Maybe I should get a whole new wiring harness for a junk yard?

Here is the subject:

 

[Brain75]

Fuel pressure is "in spec", was that just at idle?... key on/engine off is it priming up to good pressure still? does it (fuel pressure) stay consistent through rpm range when you get it started? I'm totally grasping here since you threw 2 different pumps at it, but fuel delivery issues (pump or filter) I would think would be the most common before you get started and the computers get all involved.

 

[bobbywalter]

filter in the right direction?



is it low on power? or just starts and low speeds shitty?


what is the resting tps?

and baro?

 

[Kirby N.]

thanks for the responses.

TPs reads .96 at rest

Fuel Filter is brand new. Just changed it out- forgot to mention. It is oriented correctly.

feels a little low on power maybe. Nothing drastic.

what is Baro?

yes- did all the fuel pressure tests and it was in spec. Tested with regulator unplugged and with, key on engine off, starting. Engine running. Can hear the pump prime with key on. The one I threw at it was a brand new Carter. I also put back in the new old stock ford pump when I saw the Carter did nothing. Which is what it has in it now. About a year old. Doesn’t change the start if I prime it 10 times before starting.

 

[bobbywalter]

your in colorado right?

its long crank so...

maybe something is janking up on your iac system.. check the passage in the intake....but first...

barometric pressure sensor. maybe a mud dobber packed it off or something.

you should have one on a 91....i might be remembering that wrong. its actually just a map sensor open to atmosphere so it knows elevation. figure out kpa for your elevation and whatever its reporting.... its 3 wires just like a map...because it is a map....just open to atmosphere.

should be up in the firewall and unlike a map sensor it will have a nipple protector to keep you from putting a hose on it and usually be recessed into the firewall...right next to the vacuum resevoir dealio on the hvac box.

 

[Brain75]

Just to double check that I am trying to troubleshoot a 2nd gen ODB1 and not some hybrid..... you said the block is 2000 with some 95 parts on it etc etc... is the whole computer and wiring system either stock 1991 or repaired to 1991? - you aren't trying to run a 2000 ODB2 brain box, etc etc. For all diagnostic purposes it is a 1991, just some of the dumb (steel) parts are newer.

 

[Brain75]

Monument is a high elevation city 7000' (69xx something if I remember right, basically 7k).... Another dumb question from a fellow Coloradoan at that elevation can you still buy 87 octane or are they selling 85 as the "regular"..... I've never had problems with 85 when I go to the mountains except in my old '89 tracer but that is another story.
Now the big question.... winter blends of fuel just came out early/mid October... do you notice the issue corresponding to running on summer blend versus winter blend?

 

[bobbywalter]

Monument is a high elevation city 7000' (69xx something if I remember right, basically 7k).... Another dumb question from a fellow Coloradoan at that elevation can you still buy 87 octane or are they selling 85 as the "regular"..... I've never had problems with 85 when I go to the mountains except in my old '89 tracer but that is another story.
Now the big question.... winter blends of fuel just came out early/mid October... do you notice the issue corresponding to running on summer blend versus winter blend?

excellent point. i was just through there and running rec fuel one way and some typical garf e15 the other.....holy hell the difference was astounding. 20 mpg vs 14.

in general the fuel out there is 2 mpg better quality then the garbage we have in detroit. though elevation is partial to that.

the fact that the ecm made no difference has me suspecting valvetrain or fixed idle values or improper baro reporting.

of course if its a 2000 eec5 system...whole different deal.

 

[Brain75]

I have a hunch the OP has a pure 1991 computer setup, but just want to make sure before I bash my brain too hard.

 

[Brain75]

Typically when you head into the mountains you don't run into 85 octane until idaho springs (elev 7500+). But to be honest every trip down monument hill I was just white knuckling through the blizzard hoping to get to the bottom without loosing it, not too worried about stopping to look at what kinda gas they have.

 

[bobbywalter]

yup.....i know what you mean

 

[Kirby N.]

Just to double check that I am trying to troubleshoot a 2nd gen ODB1 and not some hybrid..... you said the block is 2000 with some 95 parts on it etc etc... is the whole computer and wiring system either stock 1991 or repaired to 1991? - you aren't trying to run a 2000 ODB2 brain box, etc etc. For all diagnostic purposes it is a 1991, just some of the dumb (steel) parts are newer.

It’s all original 1991 obd1 everything. Thank you.

 

[Kirby N.]

your in colorado right?

its long crank so...

maybe something is janking up on your iac system.. check the passage in the intake....but first...

barometric pressure sensor. maybe a mud dobber packed it off or something.

you should have one on a 91....i might be remembering that wrong. its actually just a map sensor open to atmosphere so it knows elevation. figure out kpa for your elevation and whatever its reporting.... its 3 wires just like a map...because it is a map....just open to atmosphere.

should be up in the firewall and unlike a map sensor it will have a nipple protector to keep you from putting a hose on it and usually be recessed into the firewall...right next to the vacuum resevoir dealio on the hvac box.

Ah! Yes I know what you are talking about now. I haven’t checked that at all. I’ll see about replacing it.

 

[Kirby N.]

Monument is a high elevation city 7000' (69xx something if I remember right, basically 7k).... Another dumb question from a fellow Coloradoan at that elevation can you still buy 87 octane or are they selling 85 as the "regular"..... I've never had problems with 85 when I go to the mountains except in my old '89 tracer but that is another story.
Now the big question.... winter blends of fuel just came out early/mid October... do you notice the issue corresponding to running on summer blend versus winter blend?

Yes the problem is consistent with all fuel. This has been a problem for months now. I run 87 or 89 or no ethanol 87 all the time. At the pump I can get 85, 87 or 89. Sometimes I get a little ping/ pre detonation with 87 going up hills- so I run 89 often.

 

[Kirby N.]

I have a hunch the OP has a pure 1991 computer setup, but just want to make sure before I bash my brain too hard.

You are completely correct. Thank you for being willing to put your brain to it. Mine is getting sore from it.