skitour

allright so heres the new issue with my truck. So i fixed the air flow meter and got it running. It sounded great and ran fine. I broke it in nice and easy just running it for short periods at first. And then longer. And then i was revving it up to 2500 rpm for a few minutes to check my idle speed. And to my surprise as i am doing this for the second time. My car just stalls out.

hmmm thats strange i thought. So immediately i thought of the fuel pump. As i was using a used one so i took it all apart and tested the pump its still good. So i decided to run a voltmeter across the fuel pump circuit. And the pump is only receiving 2.5 V at the end of the wiring harness. When hooked up to the sending unit it reads as 0.3V off of the terminals on the sending unit cap. I also checked the continuity of the circuit and it has continuity. So i don't think its the ground.

Now i checked the circuit opening relay it is functioning properly. As well with the efi main relay. I am stumped as to what would cause this problem to arise. And am now starting to panic a little as i am suppose to be on the road driving to bc for the ski season.

If anyone has any ideas or anything at all that might help i am grasping at straws. I've just spent the last 10hours pouring over the electrical system of my car and can't find it.

Please help me.

n4ynu1010

Forgive me for asking but you are reading 2.5V on the positive wire to ground when it should be running and the pump is disconnected and the Voltmeter is set to DC Voltage ?

skitour

yep that is correct i traced that voltage back across the wiring and i believe that it is the EFI Main Relay that is causing this problem now i measured the voltage on the EFI Main Relay and the continuity my relay is good. So i decided to measure the voltage being sent to the EFI main relay.

The voltage across 2 and 4 is greater then 12V. Now that is the circuit that is open until power is ran across 1 and 3 testing the voltage across 1 and 3 i only get a reading of 0.03V barely even registered. Anyone think this could be the problem and how to find out whats causing it.

I checked the voltage at the IGN 7.5AFuse and it is greater then 12 and i checked the Engine 15A Fuse and it is greater then 12 V.

Hope this paints a better picture

4Crawler

iTrader: (3)

Well, if you have good votage at the CO relay and poor voltage at the fuel pump, then likely there is a wiring issue between the two points. Check the connections and also see if you can isolate the problem to either the power or ground side of the circuit.
http://www.4crawler.com/4x4/CheapTri...shtml#FuelPump

n4ynu1010

Those pump grounds are traditionally chasis grounds and can get dry and present either low voltage or normal voltage yet no current , either way it won't run right or not at all.
May have a broken wire between pump and fuse panel , may just be a dry connector connection (Di-Electric/Ignition Grease) at the top of the tank .
I have seen the ground for the pump and fuel gauge pulled from top of tank as well right on the flange around the pump/sending unit retaining/locking flange.
Have you tried jumping the pump at the OBD service connector to make sure it runs when you do that , if it works when you jump it then it is a control (ECM,Relay,VAFM).

Check the first page of this link :
http://personal.utulsa.edu/~nathan-b...87fuelpump.pdf

Jump it and see if it runs from the OBD , if it does then it has to be the EFI relay,VAFM Pump Switch or ign. switch other than a bad wire or ground somewhere

n4ynu1010

Also make sure your EFI Fuse under the hood is good or it will not work at all , I set ny base timing once and somehow when putting jumper in or out I blew the EFI fuse , have no idea how it happened but motor just went blah and died , spent that evening and the next half day trying to find out why no spark and then checked the EFI Fuse hehe

mt_goat

You could run a set of wires from the battery straight to the pump through a relay and have the stock relay trip the new relay. Hopefully there is at least enough voltage to trip the new relay.

skitour

So i tried jumping it allready and it still doesn't run. It shows that the B terminal in the OBD is only receiving 2.5 V. Now what i am curious about is where is the EFI Main relay in an 87 2door 4runner, what i thought was the EFI main relay turned out to be the Headlight relay. Now don't i feel like an idiot i shouldve definitely gotten some more rest. Anyone know where the EFI main relay should be.

Also on the Circuit opening relay when i turn the ignition switch and check the voltage across the terminals i receive 12.5V across STA and E1, i receive 2.5V across B and E1. As for the EFI fuse its not blown. I still have a strong spark and as for the car just crapping out i guess i shouldve said that it did happen when i jumped something in the OBD my jumper wire slipped into the wrong terminal.

I don't know worse comes to worse i will just run a new relay and use the power line off of my car audio i think a 0ga line should provide enough flow ehh.

but before i go that far i would like to check the EFI Main relay but where is it thats whats stumping me i can't find it on the Fuse box in the driver kick panel, or in the fuse box under the hood, or above the Computer. it is starting to piss me off any ideas.

n4ynu1010

You can't measure voltage across the connection to jump pump , you are trying to measure voltage across a broken line when you do that .
You have to measure from the hot side of that connector , you need to measure from the B+ connector to ground , if you have 12V then your EFI fuse is good and the EFI main relay is good as well but you have to do this with key on , motor not running.

longhungsilver

yup good info

skitour

allright thanks for all your help guys. I got it figured out it turns out that the EFI fuse holder had a broken wire well fractured wire hanging by a thread as it were and was grounding itself out on the body. All is well again don't know how that just randomly happened but its fixed and runs smoothly now.

n4ynu1010

AHA , that darn EFI fuse seems to be a problem child hehe
Glad to hear you got it man !!!!!!

skitour

Yeah its nice that it runs now but it just allowed me to notice i am only firing on 3 cylinders. I am thinking that the injector to cylinder 3 is providing to much fuel or not shutting itself off. Seeing as how i have 180lbs compression across the board. Unless anyone knows of any easier fixes.

p.s i have all new plugs, plug wires, coil, distributor cap, etc

n4ynu1010

What do you mean by not firing , no spark ?

skitour

Its the weirdest problem in the world well to me anyways, there is a good strong spark, excellent compression, there is fuel present, but no combustion happening.

So i used a stethoscope on the pressure regulator it sounds as though its functioning, i also used a stethoscope on the injectors and they all sound as though they are functioning properly.

I have yet to check the resistance across the injectors so that is the next step.

P.S. This might be unrelated but when you repeatedly press the brake pedal the engine speed slows down almost to a stall until you let off it rises back to standard idle speed.

anyone have any ideas

n4ynu1010

Brake thing is just the brake booster , you could probably block that off (pinch vacum line to booster with needle nose pliers) and see if it affects your idle , brake booster could be leaking but that is rare , I think most engines that you just sat there and pumped power brake would stumble so that is probably normal , check to be sure "never know" .
Yeah ck the injectors , if the spark timing and cam timing are right that would be the only thing it could be unless you have a cracked insulator(jumping spark to grd) on the plugs or losing spark to ground , you said you had good compression so it would have to be no fuel , other than that it is spark timing