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Hi, I bought a '93 Toyota pickup 2wd a few weeks ago and have been driving it about 100 mi a day to work. It has been running great. Sometimes i would turn the key to start it, and it will just crank and I will have to wait a little while before reinserting the key and letting it sit on position 2 for a few seconds before fully turning, which has started it up just fine in the past. Today, I went to go to work and it would not fire up at all it would just crank and crank. A few hours later I went to try and start it. It fired one time before immediately dying. Then I tried again and it started up fine and idled for about 5 or 10 minutes. Everything sounded normal, no misfires, no check engine, etc. Then it suddenly died. Didn't bog down or start missing or anything, it went from idling fine to immediately shutting off. I restarted it and it started right up and idled fine again for 10 minutes before the same thing happened. I have been searching lots of threads on here and I am thinking it must be fuel pump or something fuel related, but not sure where to start. Any help is greatly appreciated!
Update:
With Fp and B+ jumpered, I can hear the fuel pump turn on with ignition in position 2. If i fully turn the key, it fires up and starts fine, holding a stable idle. Even if I take the paperclip off, it will continue to idle well. If I try to start it without the fuel pump jumpered, it will only crank and not fire up at all.
This is leading me to believe it is a relay/wiring/fuses that control the fuel pump. I already checked the efi fuse and it looks good, however my fuse box is missing the cover so the connection points are a little bit dirty.
Hi, I found the thread you linked pretty helpful. Today I had time to do some of those tests:
Fuel pump draws 3.1 amps when Fp and B+ are jumpered at diagnostic box
12.6 volts from b+ to ground also at the diag. box
1.1 ohms Fp to ground with key off
there was no fuel pump sound when pressing vane with key on. fc and e1 are continuous on vaf with vane open
vaf connector side: fc to ground has no voltage with the key on
connector side e1 to ground is continuous.
I went through the procedure of testing the COR, and found that there was no continuity between +B and FC, when there should have been. It said to replace the COR.
I picked one up at local autozone and tested it, only to find the same thing that +B and FC was not testing as continuous. I put the new one in anyway to try and the issue still persists.
I would say yes. Having said that, are you sure the one you bought is identical to an OEM relay? Same ohm value of the coil? With the relay out of the vehicle? Same pin-out? IOW same inputs and outputs under the same conditions. OR, the same pins connecting to the same pins, when it's energized, or de-energized.
Did you set the conditions for the relay to operate correctly? It has two halves: 1 half is in operation during the start cycle, and one half in operation while the truck is running. The "start" half operates when the key switch is in the STArt position. It can be checked by turning the key to start, but not depressing the clutch, or the Clutch Start Cancel switch. basically, just listen for the fuel pump to run during that condition. The other half should be in operation when the MAF vane is open, and the key is in the ON position. Again easiest to just listen for the fuel pump to run under those conditions.
These are with the Fp-B+ jumper out, and the MAF connected normally.
Bear in mind that Toyota likes to switch ground in and out of a circuit to make things function. That's why E1 has constant ground on it: When the vane is opened, the ground on E1 is applied to the fuel pump circuit, activating the fuel pump.
You should trace the lack of voltage on Fc when the key is on.
Here's a slice of the EWD (for 1993, but almost certainly the same as yours).
So, yes, from pin 4 to pin 2 you should have continuity (though with some resistance) through the FC coil of the COR. If your relay is working, you should be able to apply 12v from 3 to 6, and separately from 2 to 4, and hear the relay click each time.
Thank you guys for the useful input. I think i am narrowing this issue down day by day. I am pretty limited to how long I work outside on the truck since it is still 110+ in phoenix all the time, but ive been chipping away on it. I just tested the fuel pump with 12v to the connector to the pump (the one right by the fuel tank). The fuel pump starts up and has good flow out of the rubber return line.
also For some reason, I can't jumper Fp to B+ at the diagnostic anymore, and I cant jumper it at the COR connector either (with key on) Could I have a broken wire from the COR to the fuel pump? I think I need to re do the tests at the diagnostic port to make sure I can trust my VAC COR tests.
I applied 12v to the COR pins 3 and 6, and 2 and 4 separately and could hear a click for both of them. Good news. I think my COR is good.
FC to ground in COR connector is continuous. No voltage fc to ground on VAF connector side. No continuity to ground for e1 (vaf connector side also)
At this point my guess is a broken wire from the COR to the fuel pump (can't jumper fuel pump from COR connector points to this) , and also a broken wire from the VAF to the COR (no voltage for fc and no continuity for e1 point to this) ? Seems unlikely these 2 wires would break at the same time.
Apologies for the unorganized post, I wanted to post some updates on the tests I have been recommended to do.
How would you recommend i trace the no voltage for fc at the vaf? I’m guessing there are two other points where the circuit can be tested at; A fuse somewhere, and at the COR connector? When i tested fc to ground at the connector it was continuous so presumably the wire to vaf is intact?
Here's a slice of the EWD (for 1993, but almost certainly the same as yours).
So, yes, from pin 4 to pin 2 you should have continuity (though with some resistance) through the FC coil of the COR. If your relay is working, you should be able to apply 12v from 3 to 6, and separately from 2 to 4, and hear the relay click each time.
I am still trying to track my issue down. Right now I have the intake manifold off and fuse box taken apart to further inspect the wiring. I only had 2.2 volts to ground at the B+ diagnostic terminal with the key on. Why could this be so low? and why not zero volts could this be a bad connection along the wire that provides power? I read somewhere that If b+ is not getting enough voltage, then it will either cause the engine to run bad / die / or not start. When I jumper the fuel pump from the battery positive terminal directly (instead of b+), I get good amount of fuel and pressure coming up the intake manifold. I am sure the COR relay is good, however I only get 2.2 volts to ground at the COR socket. Battery is good and has 12 volts.
I am a little stuck on how to trace the positive battery wire. I know that it is the white wire with red stripe. If I had 0 volts at b+ and cor socket, then I would know it is broken, but what does 2.2 volts tell me when it should be 12??
Also, I forgot to mention I have 12 v at the efi relay on both the black/grn wire and the black/yel wire with the key on. I can hear the efi relay click when I apply 12 volts to pins 1 & 2, which corresponds to the black/yel wire and white / blk wire. I cannot hear the relay click when I give 12 volts to pins 5 and 3 which corresponds to the black / grn wire and the white/ red wire (B+!) So I have good voltage (12v) at the efi realy for black/grn and black/yel, but only 2.2v at b+ on diagnostic port and cor socket.
Check the fuel pump, filter, ignition coil, and distributor. If the issue persists, seek professional diagnosis and repair. Hey, Check this https://triceloans.com/best-metal-credit-cards/ website out and Dive into the world of metal credit cards and experience a new level of prestige. The Platinum Card from American Express stands out as a beacon of luxury, offering elite benefits, worldwide lounge access, and remarkable rewards. If you're ready to embrace unparalleled style and convenience, this metal masterpiece might just be your perfect fit.
Last edited by RonaldMeredith; 08-17-2023 at 09:36 PM.
With modern multimeters with very high input resistance, it's very hard to read zero volts on an open wire! When any wire with a tiny current is "next" to an open wire, it can induce just enough current in the open wire that you'll read a voltage. If you put a relatively high resistance (~1-100k ohms) to ground, that "ghost" voltage will go away. Modern industrial voltmeters have a setting that does just that. https://www.fluke.com/en-us/learn/bl...al-multimeters
So I'm sure your 2.2v just means you have an open wire in the battery voltage side. Based on your report, I suspect that your EFI relay is closing (you hear the click) but the contacts aren't making a connection. Can you measure voltage to ground at the EFI relay at the B-G and R-W wires? If you get battery voltage on B-G but 2.2v on R-W (key-on) that points to the relay. Then a positive test would be to pull that relay out of the socket, and then just jumper those two leads (simulating a closed relay). If your problem clears up, chuck that relay in the can.
so i replaced the fusable link and the positive battery terminal and the truck ran perfectly fine for a day.
now im stranded on the side of the road 50 miles from home
while i was driving the truck this morning i died on the highway a few times but i just had to turn the key off and on.
now it will turn on and run for about 2 minutes before dying. It will start when i have 12v at b+. when it dies, i have 0v at b+ in diagnostic port. So it seems that the EFI relay works for a little while before getting too hot or something, then it pops or cuts off power down the line causing the truck to die. I’ll source a new relay this weekend but any way to bypass this to get it home?
thanks.
08-01-2023, 10:03 AM
