Hey guys,
I am kinda new to working on this truck, and the fuel system is killing me. I have a 89 pickup with the 3.0 with EFI. I had to put in a new fuel injector in the other day because one was busted and leaking fuel and pressure in the system. Now the truck would run before, but it ran like crap, being down one cylinder and all, but now it won't run at all after putting it back together. I have looked and looked for problems, but can't find any. The only thing that concerns me is the EFI relay under the hood. When I pull it out the check engine light goes out, and when I put it in it comes right back on. Something is not allowing the fuel pump to send up any fuel, any ideas? Maybe the EFI relay?
Thanks for the help.
Reply 1 : Stumped on the EFI
Suggest visiting the AutoZone website to review the wiring diagram for this truck. There could be a blown fuse, etc.
Typically the EFI relay powers a Circuit Opening Relay that actually turns on the pump. When the engine cranks a wire in the starter circuit closes the opening relay, once the engine starts typically the MAF sensor has a switch the closes due to air flow and keeps this relay on.
This prevents the pump from running when the ign key is on and engine not running.
Look under the hood for a small plastic box labeled "Diagnostic." If you have the box find the FP and B+ terminals. Jumping these terminals with the ign switch on will bypass all the relays and should power the pump.
Reply 2 : Stumped on the EFI
I have used the jumper wire already and I get nothing. Pump makes no noise, and there is no fuel to be found. All the fuses under the hood are good, I checked them today. Are there any others?
Reply 3 : Stumped on the EFI
Did you check the Fp terminal with a test light or meter to see if you are getting power when you are cranking the engine over? Which injector did you replace?
If the CEL is coming on that means the EFI relay is working and the fuse is good. Depending on which injector you replaced and how far you had tore it apart to replace the injector, I would suggest double checking the ground wires, you might have inadvertently forgot to reconnect or tighten one down.
N.E.O.
Reply 4 : Stumped on the EFI
No I have not put my test light on the Fp terminal while firing the motor, but I did check it when I did the jumper wire and it was getting plenty of juice.
I replaced the first injector on the right side of the motor when looking into the engine bay from the front of the truck, its the easiest one to see.
I did not have to tear the motor down far at all, and there were no electrical connections other then the injectors and the throttle body, and I have double checked all of that stuff, and everything else is nice and tight.
But I will give everything else another look over tomorrow. Why would the check engine light mean that the EFI relay is good and not bad, especially since it goes off when I remove it?
Reply 5 : Stumped on the EFI
N.E.O. knows what he's talking about. Just to be clear, there are two relays between your battery and the fuel pump. The relay you're pulling out of the fuse box in the engine compartment is the EFI Main Relay. It energizes the whole EFI system. Then there is the Circuit Opening Relay that toyomoho mentioned. It's above the ECU in the cab, but you can test to see if both of them are working by following N.E.O.'s advice and getting a voltmeter or test light on the FP terminal of the diagnostic box (with NO jumper attached) while someone is cranking the motor.
As N.E.O. said, if FP has power while cranking, both relays are working and your pump is getting power, and therefore you may have a pump (or pump wiring) issue. If FP ISN'T getting power, check the B terminal for power when the ignition switch is on. That's coming from your EFI Main Relay. If B is hot when the ignition's on, your EFI Main Relay is fine. If B is NOT hot, then you need to check the main relay. As you may know there's an online manual for a '93 truck here:
http://personal.utulsa.edu/~nathan-buchanan/93fsm/
This page shows where the various EFI components are located:
http://personal.utulsa.edu/~nathan-b...94electron.pdf
The fuel pump circuit schematics are here:
http://personal.utulsa.edu/~nathan-b...87fuelpump.pdf
The instructions for testing the EFI Main Relay are here:
http://personal.utulsa.edu/~nathan-b...95efimainr.pdf
If B has power with ignition on but FP doesn't when engine is being cranked, then your Circuit Opening Relay isn't closing and sending power to the pump. This could be due to a bad Circuit Opening Relay, but also it could be due to the Volume Air Flow Meter's Fuel Pump switch not closing (making a connection to ground). Check to make sure the air flow meter's connector is secure. If it is, check the fuel pump switch in the VAFM by pulling the connector and checking for continuity between the left two terminals (Fc and E1) There should be no continuity (infinite resistance if using an ohmmeter) when the VAFM's vane is closed, and continuity (zero resistance) when you push the vane open, even a little bit.
You can also check the VAFM's wiring harness connector - from the schematic it looks like the terminal connecting to E1 should have a good ground, and if it doesn't, the Circuit Opening Relay won't close to ground and power the fuel pump.
http://personal.utulsa.edu/~nathan-b...33volumeai.pdf
If the VAFM's working okay, and you can't find any other connectors unattached or bad grounds as N.E.O. suggested, then you need to check your Circuit Opening Relay with a multimeter. The specs for doing that (on a '93 truck) are here:
http://personal.utulsa.edu/~nathan-b...96circuito.pdf
Keep positive - wiith persistence and double-checking each step you will eventually find the problem and get that thing running again.
Reply 6 : Stumped on the EFI
Sorry, I didn't see your reply while I was typing mine...
If you jumped B to FP and FP was hot, then at that time your EFI system was sending power to the fuel pump and you should have been getting fuel pressure. I'd still check FP without a jumper while cranking just to be sure both relays and the VAFM are working, but it sounds like you may have a fuel pump issue. The next step may be an unpleasant one, as you'll need to check the connector to the fuel pump to make sure power is getting all the way to the pump.
And that connector is on top of the gas tank. Oops.
Depending on whether you have a camper shell, it may actually be easier to lift the bed than drop the tank.
If you need a pump, I can share some info as I just today received an AISIN pump from Rockauto. I waited to see what it came with, and it came with nada. So on top of the $144 pump, I just ordered a sock, rubber hose connector, two clamps, pump bracket gasket, a fuel tank drain plug gasket and 7 bracket screws from the dealer for $45.
While checking around at autohaus today, I found the pump I should have ordered was a DENSO pump AND KIT which included the sock and a bunch of parts for $140 total. You'll still need a pump bracket gasket, and I've been told the seven screws are very likely to be rusted. They're only 54 cents each. You may need a fuel tank drain plug gasket, too.
Anyway, I hope your pump is okay, as it's not only the expense but also the aggravation of getting to it. It would be weird if the pump just happened to fail exactly when you made a repair, of course. More likely the problem is something inadvertently introduced while working under the hood. But it wouldn't be the first time that something like that happened, either. And if FP has power while cranking, the pump is probably getting power.
Good luck and keep us posted.
Reply 7 : Stumped on the EFI
Sounds like sb5walker has got it all covered!
The reason for checking Fp for power while cranking is to confirm that the CO-relay is receiving the crank signal.
When you remove the EFI relay, you also remove the power from the ECU and its ability to ground the CEL, and that is why it went off when you remove the EFI relay.
BTW, sb5walker, thanks for the kind words.
N.E.O.
Reply 8 : Stumped on the EFI
Quote:
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Originally Posted by new echo owner 
BTW, sb5walker, thanks for the kind words. N.E.O. |
Reply 9 : Stumped on the EFI
Thanks for all the advice guys, I will give all this stuff a shot and see what I come up with. I hope like you say that it is some small electrical thing and not the pump. Thanks again, and I will let yall know what I find.
Reply 10 : Stumped on the EFI
Keep us posted!
N.E.O.
Reply 11 : Stumped on the EFI
Alright guys, I have checked just about everything on your list of suggestions and no luck yet. I am really starting to think it is the fuel pump. But just one last question. If I take a jumper wire and run it from the positive battery terminal to the fp terminal would that make the fuel pump run if it was good?
Reply 12 : Stumped on the EFI
You are correct, that would power the fuel pump directly, and if the pump is good, it should run. Checking the Fp terminal for power serve the same purpose;l if the Fp terminal has power when cranking, that means the pump is receiving power and the pump should run if it is good.
BTW, there is no last question, keep them coming as long as you have to!
N.E.O.
Reply 13 : Stumped on the EFI
Alright then, the fuel pump must be bad. The pump did nothing when I hook it up directly to the battery. Looks like I will be dropping the tank, thanks for all the help guys.
Reply 14 : Stumped on the EFI
Keep us posted on how it turn out!
N.E.O.
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