fuel pump??? 760T

A while ago the 760T started to conk out whilst driving on the freeway, not
very often, not enough to worry about. Then it had a spate of conking out
when it goes around a corner,

is it the fuel pump? which one?

Thanks in advance

 

In <D3Zwf.213270$>,

Check the FPR before the fuel pumps. This is a well known failure on
740s / 760s.

AC

 

What does the tachometer do when it stalls? Does the needle ride down
with the engine RPM or does it fall like a rock?

 

When the prepump or connecting hose between the prepump and outlet tube
in the tank fail the car will stall religiously on left hand turns from
about half empty and below. Often it will show a flat spot on hard
acceleration. If the prepump has indeed filed it would be prudent to
change the main pump as well since the repeated absence of fuel from the
preump will have damaged the bearings in the main pump since they rely
solely on fuel for lubrication.

Bob

 

I believe the tacho, just drops like a stone..

 

A common cause of ignition cutout (which will be the case if the tach does
drop like a stone) in that vintage is the Hall effect sensor. IIRC the part
runs a little under $200 US, but I lost the list Mike F posted so long ago
about which model/years had the sensor in the distributor and which had them
at the flywheel. The sensor can be very difficult to catch in the act, and
many are diagnosed on the basis of "changed it - no more problem" or
"changed it - still have problem." Symptoms are typically engine cutout any
time it wants for as short or long as it wants, although some fail
completely.

If the fuel pump is quitting the power will disappear somewhat smoothly, but
if the ignition is quitting it jolts off and on - assuming there is an "on"


Mike

 

It's not a fuel problem then. My first guess would be the hall sensor in
the distributor, or depending on the year it could be the problem I had,
a crumbling wiring harness. It's also possible the ignition power stage
is failing.

 

Yikes, no you can order the hall sensor for about $45, not nearly so
painful.

 

Turbos had the hall sensor up to and including 1989 model year (up to
and including 1988 for non turbo).
The ignition power stage is mounted on the inner fender on an aluminum
plate just behind the left headlight.
If your car is post hall sensor, the part that replaced it, the crank
position sensor, suffers from similar problems. It's located in a
bracket on the top of the bell housing.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

That's good to know - it puts it in the range of being "shotgunnable"
(replacement on suspicion). Where's a good source? I looked at IPD but
didn't see it.

Mike

 

Both FCP Groton and alloemvolvoparts.com sell it I believe, I know at
least one of them does. I forget who is cheaper but I shop between the
two depending on what I'm getting.