No Start , Jumped +B and Fp, now starts fine without jumper wire (1 Viewer)

[huntingfor62]

Long story short:
I have an 88 FJ62 that was cranking but not starting. Check engine light was off. After a week of fiddling around and researching the FSM and this forum, I jumped the +B and Fp contacts on the diagnostic connector. Thought I heard the fuel pump so I started the truck. Truck started fine with the jumper wire. After taking out the jumper wire, I decided to start the car again. The car started perfectly. I've now started the car several times in the past hour without the jumper wire. While I'm happy that the car starts without assistance, I'm worried I haven't solved the underlying problem or worse, I've ruined something electrical. Any insight is greatly appreciated. Thanks!

Background:
I'm a novice with mechanical work. Recently replaced my AC evaporator, cleaned the AC ducts, and converted system to r134. During the process I disconnected and reconnected the evaporator box, ECU, gauge cluster, and radio. I also removed and replaced the dash pad. Shortly after AC work, I drove the car on a 120 mile trip. My 62 then sat for a week before I tried starting up again. That's when my crank/no start problem began. During diagnostic for crank/no start, prior to jumping +B and Fp contacts, I pulled the EFI main relay and applied voltage across terminals 1 and 3 and heard a click to I assumed relay was working.

 

[Prairie Swamp]

Purely a guess - without looking at the wiring diagram - something is failing and getting "sticky". Maybe a relay is failing and the voltage drop of all the wiring and contacts through the ignition switch etc made the voltage so low it couldn't bring the relay in.

The jumper in the test connector bypasses all that so maybe it brought the voltage up enough to get the job done.

I'm not telling you to swap stuff out without knowing what's wrong. But I think you'll have the problem again especially after the truck sits and doesn't get exercised. Sounds like a sticky relay maybe fuel pump.

 

[huntingfor62]

Purely a guess - without looking at the wiring diagram - something is failing and getting "sticky". Maybe a relay is failing and the voltage drop of all the wiring and contacts through the ignition switch etc made the voltage so low it couldn't bring the relay in.

The jumper in the test connector bypasses all that so maybe it brought the voltage up enough to get the job done.

I'm not telling you to swap stuff out without knowing what's wrong. But I think you'll have the problem again especially after the truck sits and doesn't get exercised. Sounds like a sticky relay maybe fuel pump.

Thanks Prairie! For next steps what items should I be testing? EFI Main Relay, Circuit Opening Relay, fuel pump? Any other relays? I was also thinking of purchasing a better battery. Would that help at all?

 

[toyotaspeed90]

You are bypassing 2 things when you jumper b÷ and FP (which provided power directly to the fuel pump).

One is the air flow meter. It has to be open far enough (via vacuum - aka the engine pulling air in kind of like if you were to suck on a straw) to send a signal to turn on the fuel pump. It's common to have vacuum leaks where the engine can pull air through cracks in tubes or missingvacuum hoses - which means the air flow meter gets bypassed.

The other is electrical - which is the circuit opening relay. I believe I've read in these rigs those are located on the passenger kick panel.


If you have problems starting again without the jumper - pull the air filter and push open the air flow meter flapper and listen for the fuel pump. Ypu may not be pulling as much vacuum when.its cranking while cold - which could be the difference.

 

[cruisermatt]

It’s also possible you have a wire chaffed somewhere.

 

[huntingfor62]

Thanks for the info guys. I found out the problem. I guess it was the EFI relay. Even though it clicked when I applied voltage, not enough current was flowing through it to start the car. I replaced the relay and its starting fine now.