SOLVED!!! I can now get fuel to the engine. Won't run long - 1987 740

Check the ground wires and such in the trunk, you might have a loose one or a chafed wire or something, I don't like problems that just vanish like that, usually they come back at the most inopportune time.

Ground wires are funny, James. Couple weeks back I spent 3 days chasing a gremlin in my folks 1988 Toyota Land Cruiser.

Headlights went out - taking with them, the blower motor, radio, power antenna, cigarette lighter.

I had all headlight wiring inspected, rear lights pulled, yanked the dash out. I pulled the steering wheel off, removed the steering column and turning assembly. We spent $35 on a new headlight dimmer switch (Rheo stat switch). I pulled wiring diagrams off the Internet and checked every darn fuse link under the hood.

FINALLY, after dozens of posts on a forum, some guy says, "oh - that happened to me. go and tap into the ground of the cigarette lighter and ground your new wire into the chassis."

AND THEN THERE WAS LIGHT!!!!!! That fixed everything.

Just curious - do you know if the entire fuel system - or should I say both pumps - ground in the trunk? I'm wondering if it's a show stopper. Guess I could pull that ground to check.

Thanks. Jamie

No idea where the main pump grounds, I think the prepump does ground in the trunk though, it's all right there under the cover.

yeah - today i did 2 things - replace the rubber hose from the tank to the metal tube on the fuel line - and better support the contact wires to the main fuel pump.

Now, my main pump doesn't fire.

Must be a short somewhere. The relay is clicking and the fuses are OK.

If there was a short the fuse would blow, must be an intermittent connection. Time to get out the multimeter.

Keep in mind the relay is actually two relays in the same enclosure, it's possible the one for the pumps isn't closing, I'm not sure what the other one does.

I'll check the voltage. My old pump has the two snap on wires, where the replacement was bolt on. I need to check voltage coming out of the wires first, and if that's good, I need to also check my rebuilt snap- on wire connections. I have about 3 relays I'm cycling through to test.

jamie

Looks like I am getting voltage through the wires when cranking. I'm also getting continuity through the red/black wires - even with the relay out.

Think I should be getting continuity when I use the multimeter on the pump wires -- off of the pump?

Yes, the pre-pump is on the same circuit.

Hmmm. Well, the only time I got a good start, the pre-pump was disconnected and I had the multimeter in the trunk measuring the voltage to the pump wire, while grounding the other terminal.

The car starts. I re-wire the pre-pump and the car still starts and runs fine.

Now, no start.

Back to the trunk to disconnect? I need a snap-on connector there. I'm tired of cutting and splicing wires there over and over to test.

I disconnected the pre-pump again - no main pump still. I put my snap- on connector back for the pre-pump, so that will be faster now.

I just need to see why my main pump is not firing.

Ran some wire to the main pump terminals and hooked those to the jumper cables. Couldn't get the pump to fire.

hmmmm.

Where's the original connector? I thought you grafted the connector from the old sending unit to the new one. Did you cut the wiring in the car itself? Butchering that is a no-no.

Pump is bad then, if you're sure you have power to it. They can fail intermittently.

The 1988 sending unit had a different snap on connector than the 1987. All I did at first was snip-off this connector (at the end opposite the unit), so that I could wire it to my car. Kind of like different trailer hitch wire connectors - you have the same wires, but the plugs are different. So, what I ended up finally doing is using the connectors from the original unit. I put the original male connector wired to my car, and the female wired to the unit and all the pretty wires match. The ground was the same - run to a bolt on the trunk floor.

I'm going to pull the pump off today and bench test it. Then go to the parts yard to get a used one. If I bench test the used one there and it works, and I bring it home and install it and it works, and everything works - that should fix the problem.

Then I see about buying a new OEM pump for the long run,

Gremlins man! They're like bed bugs -- close your eyes for a second and the buggers bleed you dry!

jamie

I ran to the boneyard for lunch. I pulled 2 pumps off 2 cars in 10 minutes. Only 1 worked on the bench test, so I brought it home and will hook it up after work.

I hope junkyard Volvos don't have AIDS. I cut myself every time I pull parts.

jamie

Ratz... I almost jumped in on this thread/problem earlier, might have saved you some grief. When I was chasing a fuel problem in my '83 245, I started with the obvious... fuse, relay, fuel filter, etc. Similar deal, Fired up after installing the new relay and ran good enough to strand me on the way to work.

The main pump was bad but as you've seen, it will still work intermittently.

My first clue should have been, several times over the course of a couple months the car would start second click as always. While I'm idling, putting on seatbelt, checking mirrors, adjust radio, etc., the motor would die. Just like someone switched it off. Crank and crank and no fire. Sit and grumble about not having looked into it the last time it happened, wait a while and it will fire up. It finally quit for good $160.00 in towing from home. Put a new pump in and all is well.

That all makes sense Clay. Here's the weirdness of my situation. The car (1987 740) is for sale. I really put a lot of time and effort into this car, it looks great, runs great - it's really clean. I work for a university and will probably take about a $1500 loss so that someone's kid gets a good commuter car.

Anyway, I have it by the road, the for sale signs are up, and the ONLY thing it did wrong was make that brief stall in turns with less than

It always started and ran well. But, I couldn't sell the car knowing it did this - so I wanted to make it right.

Lo and behold - the Gremlins came a running and I sure hope the new pump is the cure all.

Thanks! Jamie

Not sure if you are interested at this point, but somewhere on Turbobricks(know that is not as good as a URL) there is a see and tell on how to replace the original main pump with a pump that eliminates the need for the intank pump and if I recall correctly at a very favorable saving in change compared to a replacement.

joe