zerokelvin

Thanks for the diagrams RAD. I'm out of ideas and have replaced pretty much all the components. Coil, igniter, ECU, ignition switch, distributor, spark plugs (more than once), battery, all fuses, tested all relays. I didn't replace the AFM or the TPS as I was told that neither of those would keep the engine from running... is that true? If not, I'll be replacing them. Any ideas what to look for next? I'll post what I find out about the injectors likely tomorrow. I know the injector plugs are sending power during cranking/starting as I tested with noid lights. Is it possible I'm losing the injectors AFTER it starts for some reason?

Here's a couple pics of her sitting.... and the distributor. You can see the bearing seal/cover has come off and there was all kinds of metal shavings, like powder in there sliding around when I shifted the distributor... glad I got a new one even though it didn't solve the issue.

akwheeler

Check Rad's wiring diagram that he posted, at the ignition switch do you have 12 volts on the white wire and the white/red wire all the time?
How about the black/yellow and the black/red wire, do you have 12 volts there when the switch is in the "run" position?
with some solid information maybe we can help. One step at a time.

zerokelvin

I'll check the power to those wires akwheeler. I'm colorblind so it'll be fun Certainly has been one step at a time for the last few weeks. It will run eventually....

zerokelvin

Checked all the wires and have power in the correct positions. I just replaced the fuel pressure regulator and got a new AFM as mine failed one of the ohm tests. After putting the new AFM on, tried to start it... nothing. I noticed that NOW the fuel pump is NOT turning on with the key in the ON/RUN position. Swapped the old AFM back in to see if that caused the change... did the same thing, fuel pump not turning on in the ON position. I also don't hear the COR clicking.... what happened? Rechecked all fuses and relays thinking something maybe popped... all were good. I'm lost.

akwheeler

Back to square 1, the drawings that Rad included should help you out. find the check connector and jump B+ to FP (see the drawing) or run 12 volts positive to FP and see if the pump runs.

zerokelvin

Will do. Been busy with other stuff so I didn't give her any attention today. I'll be back at it tomorrow. I'm not very knowledgeable with fuel pumps and had a question which may or may not be related... anyhow: Is the fuel pump a type of device that can get worse and worse and THEN stop working OR is it the type that work at 100% function THEN just stop working all together?

RAD4Runner

Zerokelvin, did you trace wires from fuel pump, along door threshold to COR to verify wiring is stock?
With stock wiring;
1) Ignition to START,
2) Starter relay will click and crank starter, and turn on CSI IF cold.
3) COR behind glove comp will click, and fuel pump wil run.
4) You get spark, and VROOM.
5) If VROOM stays and keeps AFM flap open, AFM contacts (forgot which pins) keeps second coil of COR on. Then u can release ign key and VROOM stays.
6) If second coil of COR does not stay on, when u release ign key, COR will click again (this time opening contacts and turning off FP.)
How does your truck differ from above events?

Good question that I meant to ask fellow members, so we can decide whether to prepare a spare at a certain mileage, OR replace it at a certain mileage as preventive maintenance.
To those who had first-hand experience with failed fuel pump,
1) Did you sense warning signs, like hesitating as if starved of fuel, low fuel pressure actually read at gage on the rail?
2) At what mileage/years did the pump fail?

Fuel pump on our 1987 Prelude just failed without warning. I think it was carburated so I did not know if it was a mechanical or electrical pump.

Meanwhile, when you're feeling frustrated and need a break, Here's recreational reading about a fuel pump adventure from no less than Yotatech's very own Defrag (Home on the Highway)

akwheeler

I have plenty of experience with fuel pumps, mostly with other brands, and yes they can fail either way (warning or no warning). Often it seems that if you were to check fuel pressure often enough that you would probably see a loss in pressure before the engine shows any signs of a problem. But that is not common, people drive until they see a drivability issue like a complete no start situation and then find out the pump failed, so it appears to be an instantaneous failure. Many people don't notice the warning signs. It all depends on whether the failure is in the brushes and motor windings (no warning) or with the internals of the pump gears (pressure drop). One trick I was shown with Chrysler minivans was to bang on the bottom of the fuel tank while cranking the engine, often the fuel pump would start working again long enough to pull the car in the shop without a push and was usually caused by failed brushes in the pump (once shut off it wouldn't spin anymore but with a wake up call it would start working). with natural wear an older fuel pump will supply less pressure than a new one, so checking with a gauge isn't a great way to determine when to expect a failure. But if it is not meeting the specified output you should replace it, even if the engine is still running flawlessly it is only a matter of time. as to mileage, I have seen pumps fail at 60K and I have seen them still working at 200K, so it is just something to deal with when the time comes.

zerokelvin

So, My brother is on a motorcycle trip across the USA (2nd time doing a trip like this) and he stopped by. He's an Electrical Engineer and the Director of global service and support for Accuray Inc. He did a ton of testing to help me out. He said all the components are fine and the fuel pump is also fine. He ran a long wire from the positive battery to the positive terminal on the pump and ON it went. So I've got to basically inspect all the wires connecting all this stuff for the ignition and fuel.... something is broken, shorted, etc somewhere.. just gotta find it.

thefishguy77

iTrader: (1)

That was my problem and it was in my injector wires

David Makizuru

old87yota

This has not been confirmed to be the problem yet.....

zerokelvin

I don't know of any relay on the passenger side kick panel. All I saw was the ECU, the COR and a big bundle of wires...

I'm replacing the wiring harness as all my testing shows a short somewhere. Guess the entire system is getting power, just not enough to operate... about 7V and drops to 5-6 V all over when cranking. Anyone happen to know how many Volts it takes for the fuel pump to run? If the wiring harness doesn't solve the issue then I'll be taking out all the wires in the truck and rewiring the whole thing, which will leave the truck in the garage for a long time...

akwheeler

12... it's a 12 volt system. with the engine running it should be over 14 volts. on just the battery it should be over 12.5 volts.
connect the negative side of a volt meter to the negative side of the battery, touch the positive to the battery positive and read your battery voltage, then follow the circuit and see where it drops, that is your problem area (connector/relay/splice etc.)
you CAN fix this without throwing parts at it, but you will have to have a wiring diagram, a meter and be systematic about what you are checking.

zerokelvin

Thanks for the post akwheeler,

Battery testing at 12.8 V. I know I can fix it without throwing parts at it. I would have to remove the wiring harness to do this and pull it all apart and find the short/problem. I found a harness on ebay that I'm trying to get for 100 bucks. To me it's worth 100 bucks instead of pulling that mess apart, locating the issues, fixing issue and setting the harness all back up. I saved a TON of money by doing this whole project myself so I don't mind throwing a few hundred at it here in the home stretch. Hopefully it will start with the new harness...

zerokelvin

I would love it if someone had a LABELED diagram of the engine/injector/etc wiring harness to be sure everything gets hooked up and plugged where it needs to be.

RAD4Runner

That's it the Circuit Opening Relay. I explained above how it is wire and how it works.

How sure are you that the new harness is not defective? You could end up troubleshooting another part. If you plan to work on the truck yourself, might as well go through the existing wiring to understand the system better and to really find out exactly what's causing the problem. It's like if you want to navigate a place well, best to do the driving yourself rather than hire a cab.

7V too low.
Have someone crank while you measure voltage at fuel pump.

If it does, then it's like you were taken to a place blindfolded; you never really know how you got there. How would you get home?

zerokelvin

Understood Rad,

I forgot the COR is a relay lol. COR is good so that's off the table... wiring to COR etc could still be the issue however.
I'm not sure the wiring harness if defective. However, I have replaced every fuse, relay (that tested out bad) and component so the only thing left is the wires that connect them. That's why I decided to get a new harness.
"7V is too low" roger that! I did have my brother crank while testing power to fuel pump... it dropped to around 5V (I imagine because the starter is drawing a bunch of power at that time). Also ran a line directly from battery to fuel pump, it stays on all the time. Tried to start the truck that way to see if it was a fuel delivery issue... didn't start.
I do plan to understand how the wiring works with all the components. I will be removing the old harness and inspecting/testing it. I haven't bought a new harness yet, just put in an offer on a good one for a low price... we'll see if the guy accepts. Seems harnesses, even used, are a bit pricey, so I may end up fixing mine (if that is indeed the issue) if the guy doesn't accept the offer.
I also talked with my brother, the EE. He said there is "likely" a short somewhere in the harness. He told me to take it out and find the short or broken wire, etc. So I either get this harness for a cheap price and swap it out or fix mine... I'll update when one of those has been completed.

old87yota

Even though it may seem easier to test the harness when it is out of the vehicle, I would advise against removing the wiring harness to test.

There is a good chance that the problem may "fix itself" during the process of removal. If a connection is bad, moving the wires around when removing the harness may make a good enough connection to show up fine when testing the harness outside the vehicle but the connection may fail again when reinstalling or shortly there after.

zerokelvin

Thanks old,

That's great advice. I'm sure the problem came from exactly that. The engine wiring harness is the ONLY wiring I touched, moved, bent, snaked, etc, etc during the rebuild process. It might just be pinched or bent somewhere. Thanks for the input.