dgomes

I have an 87 4runner 22RE that doesn't like to start in the cold, from just above freezing and below. The fuel pump doesn't turn on. I have a jumper made up that I put in from my battery + to the FP terminal in my test socket by my fusebox under the hood to manually power the fuel pump and the truck starts just fine. I can usually let it run for a few minutes and then take the jumper out.

What sensors are affected by the temperature that control the fuel pump turning on?

I have replaced my VAF meter already. I thought it was freezing and not opening to allow the fuel pump to turn on. I believe that when you crank the engine the flapper is opened by the air coming into the engine to say fuel is needed and the pump turns on, right? I can't see that the Circuit Opening Relay could be affected by cold, it should work or not. I have also tried a different ECU and that didn't help the problem either.

Help please..

Thanks

87 4runner 22RE
268 EB cam
pacesetter headers/2.25" exhaust
magnaflow cat and flowtech muffler
31x10.5x15 Dayton Timberline MT
15x8 AR767 rims

timebandit

Uh no, the circuit opening relay has a coil for start and another for run. Check the start coil in the relay and the voltage going into it from the key switch start position when it it cranking over. I have had that happen before on these. If I push the trap door up with the key on it will start up every time.
Relays fail in a lot of different ways. Some strange.

norcalsvx

it was 19 degrees at my place and mine fired right up

Bigblock

Mine did this but my windshield was leaking slightly.Anyway the water would drip into the fuel cut relay and freeze over night.I took the relay out and found it to be full of water.I siliconed the relay and the windshield to fix it.

timebandit

Thats also possible. Mine fires up when it is 5.

dgomes

Where would I find the fuel cut relay? Is it in the fuse panel by the drivers left foot? Is it the circuit opening relay above the ECU by the passenger right foot?

I do have a leaky windshield that I am thinking about replacing also...I have already siliconed it and it still leaks. The folks at the glass shop said that silicone was about the worst thing I could do to my windshield but I thought that they were just trying to make a sale. Maybe they were right??

Thanks for the quick responses..

timebandit

Above the ECU.

dgomes

Well.. I changed the circuit opening relay and am still having the problem. Maybe I will look at the Cold Start Time Switch/Sender next. I was reading about that in a couple of other recent posts. I also have another ECU that I will swap.

Thanks for the help guys!!

spudrunner

Yes,check the Cold Start Time Switch/Sender. It has been below zero here the last few nights and my 22re and my 3vze started right up. Also try putting some Heet in your fuel tank to absorb any moisture in your fuel system.

dcg9381

You were right to suspect the AFM. The fuel pump doesn't actually go on until you start pulling air into the motor.. It could be that the flap isn't opening.. Hard to say for sure without testing it.

dgomes

I have tested my AFM and also swapped it out with another one that tested good. Still no luck. I am on my way out right now to swap the Cold Start Time Switch/Sender. I do know for sure that the fuel pump is not turning on but when it gets warm it works alright. I just need to find the part that is getting affected by the cold/damp.

thook

Cold start time switch....I'll betcha.
Mine went out a long time ago...around 130k mi. Bypassed it with a toggle switch and ground to the battery.

dcg9381

I dont think the cold start switch has anything to do with the fuel pump turning on.

thook

No, it doesn't. But, it affects cold temp starting. The AFM is okay, the COR switch is okay, what else could it be. There aren't that many sensors on there. Unless! It's the ECU..... Still, correct me if I'm wrong, but the only thing that would prevent the fuel pump from coming on when you turn the key is the COR switch.(Well, besides wiring and/or the ECU and/or the pump) ???

Targetnut

If the circuit opening relay does not activate while cranking and you have replaced the relay with no change, then you should be checking the circuit from the ignition switch to the relay that is supposed to activate it when you are cranking the engine.

I've seen ignition switches go bad in a manner that would keep one part or the other of it from working dependent on temperature.

dgomes

Alright.. I went out today to find this problem. Guess what?? The truck started right away. It's kinda hard to find something broken when it works right, uugghh. Anyway, I bought a can of electrical contact cleaner and am going to clean all the connections to the ECU, AFM and Circuit Open Relay..We'll see what happens.

Thanks so much

timebandit

I am beginning to wonder. You see the problem with anything that runs but doesn's start.

dgomes

The problem is intermittent. Sometimes it starts, usually when it is really cold or damp/cold it does not. Today it was just below freezing and it started fine. First thing in the morning when it is cold it does not, I have to jumper the fuel pump to start it and then I can take the jumper out when it is warm. I can usually drive into town, turn the truck off and start it back up during the rest of the day provided it doesn't sit for more than 2-3 hours and is really cold. I do not have this problem when it is warm out.

timebandit

Your telling me the fuel pump has to be hot wired to start a cold engine. It is possible that the fuel pressure is a little to low to start a cold engine. But in your case it is obvoisly electrical. You may have low voltage at the pump, possibaly from a bad connection somewhere. The power comes from the EFI main relay first, that goes on with the key, than goes to the CO relay, then to the pump. I had this problem with the Blazer once, only worse because the SCPI won't take any s^@t at all.

If you are jumping from the diag connector (FP terminal) than that bypasses the 2 relays I mentioned before. That should narrow it down.

84sr5yoty

Keep in mind that when you short the fuel pump test jumper, you are bypassing BOTH the AFM fuel pump switch AND the circuit opening relay. I've never seen or heard of the fuel pump switch in an AFM failing intermittently, they either work or they don't (or the switch gets stuck in the "On" position and the fuel pump runs continuously), so that points to either the circuit opening relay or the cold start injector time switch. Maybe both if you have my kind of luck


AFM testing procedure

http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml