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

OK - problem solved!

I'm still trying to figure out how, though. Too many variables to
isolate.

Recap of last 24 hours-

Yesterday:

Put old fuel pump back on. Car started, ran rough, died. Car would try
to start, but was fuel anemic. Returned AutoZone pump for $115 refund.

Last night I removed the in-tank sending unit (for about the 5th
time). I attempted to swap pumps with my old in-tank pump, but broke
the terminal bolts. So, I put the pump that came with the sending unit
back on. I checked all the wires, checked the accordion tube for
leaks, checked the wiring. Went to bed.

This morning I dunked the sending unit in a bucket of water, used
jumper cables and powered up the pump underwater. Water poured out of
the pump nicely. I hung pump to dry all day.

This afternoon, I came home, made sure the in-tank unit I wet was dry,
then I dunked it in a bucket of gasoline to displace any water. I
replaced the in-tank unit on the car, but did NOT wire it up.

Tried to start car - again it tried to start but would not.

Called wife to turn key while I put ohm meter on in-tank wires. She
turns the key while I have the leads connected to power and ground
wires in the trunk -- Car fires up nicely!

I'm thinking WTF? No in-tank pump wired, and it's running well!

Stop the car, wire up the in-tank unit, start the car - both pumps
running nicely. Drove around the block with no problems.

SUMMARY -- NO IDEA WHAT HAPPENED, BUT IT WORKS!

Thank you all and I welcome any comment on this matter.

Jamie

In sum: we have original main pump, new main filter, new sock filter,
replacement in-tank sending unit from a 1988 (that's not supposed to
fit a 1987 - but it's only wiring).

I KNOW! -- Instead of using Vaseline to lube the in-tank unit through
the o-ring, I used BOUDREAUX's BUTT PASTE!

Honest to God I did!!!!!

Jamie

 

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
1/4 tank gas.

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