Truck is a 1990 Ext Cab pickup. Sat for 2 months while I'm gathering parts for a new engine. Went to start it the other day to move it into the garage. No start. Solid cranking, no start. Checked for spark. Spark seemed fine. Fuel in tank. Fuses all good. Jumped the diagnostic port to look for codes. No codes. Jumped the B and FP connectors in the diagnostic port. Fuel pump hums nicely. Called it quits due to the heat. Did a bunch of searches on Mud and elsewhere. Was about to change fuel filter, check MAF, check cold start injector, and check Circuit opening relay. Decided to jump the B and FP connectors again, and then try starting. FSM did not indicate that as a possibility, but it worked. Started and ran fine and made it into the garage. Am I correct in assuming that the MAF is working fine and the COR is clearly not? COR is the original, 34 year old one, I'm pretty sure. Cold start injector doesn't need to work, because it is too hot right now. The COR is one of the few things I don't have 2 of, so I can't throw in a spare to test. Let me know if I am off track or should look at other issues in the starting system.
22RE No start - COR? Confirm diagnosis.
- Thread starter jgranthevagrant
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Most likely the other way around. Shorting B and FP bypasses the COR to run the pump. If the pump runs and truck starts with B and FP shorted, but doesn't start otherwise, then you probably have a bad relay.
Also, we don't have a MAF. We have an Air Flow Meter (AFM). When you crank the starter you pull air through the meter. The meter then sends a signal to the COR. So while the issue could be the AFM, in reality it's probably the COR. This is a safety feature to keep the fuel pump from pumping fuel under the hood should you get into an accident.
If I remember correctly there isn't anything special about the COR. I've heard people wiring in a standard Bosch relay.
- Thread starter
- #4
Yes, it was late so I mixed the terminology. FSM calls it an AFM. I didn't try jamming the AFM open yet, because the goal was to get into the garage and start pulling the motor. I will revisit this once I have the new motor in place. I have 2 AFMs, so I can swap if necessary for an easy test. I will start looking for the COR as well. They look fairly expensive after a brief search. But the first one lasted 34 years, so probably worth it. Thanks for the replies and info!
Imo, I’d troubleshoot it before putting in a fresh motor. The fresh motor just adds extra variables when making sure the issue is fixed. Plus the first 20 minutes is the most important part of the break in for the new motor from what I’ve been told.
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- #6
Motor is almost out. I have to keep moving because I have time to work on it right now. When motor is out (tomorrow), I might have some down time while I'm waiting for parts, so I will be taking a close look at wiring when I'm standing in the engine bay. I expect to have two weeks of downtime waiting for parts, as I have to run around to get parts over the border. I'm hoping the fresh motor will eliminate some variables like low compression in cyl 2, leaking rear main, leaking trans input, roasted clutch, etc. I recently moved and used the truck to tow a trailer over one of our bigger passes about 50 times, so the truck took a bit of a beating.
- Thread starter
- #7
Had some time today, so I went looking for the COR. Can't find it. I found it in the FSM in the wiring, and Toyota DIY. Should be part number 85910-35010. Also matches Roger Brown's writeup. I can't physically locate it inside the truck. Any pointers before I disassemble further? I found the heater blower relay above the ECU, but I don't think that is related, unless it acts as a relay for the heater blower and the fuel pump?
- Thread starter
- #9
thanks Gnob. I will take another look. Glove box and passenger speaker are out. The relay block with heater relay and 2 fuses are easy to find. any chance mine is different because it is a Canada model ext cab pickup?
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- #10
Found it last night. Got fooled by the relay facing away from the cab. Have not tested it yet, but it sure looks rusty and crusty. Will probably be replacing it, and if it does still work, it will become a 34 year old spare. Thanks Gnob. Diagram was very helpful. Is it from the electrical fsm or some other source?
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- #12
Ok, I'm back on this thread. Intermittent no start. While I had the engine out, I replaced the COR. Looked at as much of the engine bay wiring as possible, without taking it all apart. Checked continuity from start relay (driver's side kick panel) to small plug on starter. Continuity was good. Started and ran new engine for break in and TPS, idle and timing setting. Maybe 30 times? Seemed fine. Test drove about 20 ks and parked outside garage so I could clean some of the mess out of the garage. Tried to start, no go. Used jumper wire from starter to battery directly. Starts immediately. Pretty sure I can hear the fuel pump working from inside the cab. Will start trouble shooting again on the weekend. If I'm reading the FSM and EWD correctly, the following are involved in the starting system:
Starter - pretty new Denso. Works fine from battery directly.
Little plug for wire to starter - got a new one, but contact might still be a problem.
Wire from relay - checked continuity and it's good.
Starter Relay - green, above kick panel, driver's side. Very new. OEM.
Ignition switch - pretty new, OEM.
Clutch pedal switch - pulled it and checked it. works. Pedal contacts fine.
Cold start injector - pulled and had tested and cleaned during motor build.
Temperature sensor for ECU - green plug, front of intake. Brand new OEM.
EFI relay - silver in engine bay fuse box. Pretty new OEM. Will pull and check it anyway.
Things I will be checking:
Start injector time switch - Black, on front of intake. Have at least 2, but both are probably 30+ years old. Will test.
AFM - will try various things, including jamming it open. Have 2, but both 30+ years old.
Ground points - especially in cab ones. Cleaned and redid most engine bay ones when I did new engine.
Wiring - would like to not tear the harness apart before spring.
Anything I might be missing? Starts and runs perfectly until it doesn't start.
Starter - pretty new Denso. Works fine from battery directly.
Little plug for wire to starter - got a new one, but contact might still be a problem.
Wire from relay - checked continuity and it's good.
Starter Relay - green, above kick panel, driver's side. Very new. OEM.
Ignition switch - pretty new, OEM.
Clutch pedal switch - pulled it and checked it. works. Pedal contacts fine.
Cold start injector - pulled and had tested and cleaned during motor build.
Temperature sensor for ECU - green plug, front of intake. Brand new OEM.
EFI relay - silver in engine bay fuse box. Pretty new OEM. Will pull and check it anyway.
Things I will be checking:
Start injector time switch - Black, on front of intake. Have at least 2, but both are probably 30+ years old. Will test.
AFM - will try various things, including jamming it open. Have 2, but both 30+ years old.
Ground points - especially in cab ones. Cleaned and redid most engine bay ones when I did new engine.
Wiring - would like to not tear the harness apart before spring.
Anything I might be missing? Starts and runs perfectly until it doesn't start.
if it won't start with the switch but starts jumping the starter, it something in that circuit. period..
im pretty sure these starter relays are wired the same stupid way with the switch running both sides of the relay instead of separate sources.
wire in a relay for testing
im pretty sure these starter relays are wired the same stupid way with the switch running both sides of the relay instead of separate sources.
wire in a relay for testing
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What Gnob said. You have something goofy going on between the key and the starter. The starter relay appeared on these trucks in 1986. It could be that simple. Some folks have "fixed" the starter relay by wiring in a simple, cheap, Bosch-type relay.
- Thread starter
- #16
I can rule out the 30 yr old start injector time switch? Or any other old component going bad? I think I read about putting in a separate relay in another thread. If I put a relay between the ignition switch and the starter, does it bypass and eliminate the clutch start switch and the clutch start cancel switch? I never use the clutch start cancel thing. I will look around for a cheap Bosch relay. Might not be that easy to find, as I am not in an urban area.
cold stsrt switch doesn't really do much. it only activates when the key is in start depending on the temp.
the easiest thing to do is add the relay near the battery. use the old starter lead to actuate the relay and pull the starter feed directly from the battery with a fused wire.
you wire out the clutch cancel at the pedal. cut the wires of the pedal switch side and loop them.
the easiest thing to do is add the relay near the battery. use the old starter lead to actuate the relay and pull the starter feed directly from the battery with a fused wire.
you wire out the clutch cancel at the pedal. cut the wires of the pedal switch side and loop them.
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Have you done the starter relay fix yet? My truck was experiencing this exact issue and I added a fused line directly to my starter relay which solved everything. I can elaborate further if you want but there are a few good threads out there describing it in detail. It’s worth a try, it’s super easy and practically free. Hope this helps.
- Thread starter
- #19
It snowed here yesterday, so the truck work got delayed due to installing snow tires on another vehicle and a bunch of snow and firewood related work. Looks like installing another relay is easier than rebuilding the whole start system with new wires. I will try to look around locally this week for a relay. Saw one in a Ford video, but it was gigantic. Other issue is my start battery is now on the right side fender arch, near the intake. House battery is where the start battery used to be.
you don't need a ford solenoid. you aren't adding the relay to battery cable side. you are adding it to the solenoid side. you need a standard 30A relay.
