Relay Location 740?

Good day fellow aficionados of the Brick!

I have a 1985 740 GLE, 5 speed, B230 normally aspirated.

It has an intermittent no start/ stall. Suspect fuel problem.

I am looking for the relay for the fuel pumps.

I know there's one in the center of the dashboard in the relay panel.
Large white one at the left of the relay panel, second row back.

Haynes (ew) manual says there is a second one under the hood but I
can't find it.

Can someone tell me if there is one and where it is?

TIA

jimB

 

There's only one fuel pump relay, it's the one in the console.

I feel like a broken record sometimes, but if you haven't replaced the
engine wiring harness, do that first. 90% of the intermittant engine
problems I see in these cars are from rotting insulation in that harness, up
until '89 or so they simply *all* rot, and any still running on original
harnesses are running on borrowed time before they have weird unpredictable
problems or leave you stranded. When I cut mine open, it was a big bundle of
bare copper wires in a cracking outer sheath full of insulation dust. I
rebuilt it on the street by soldering new wires to the original connectors
using heatshrink tubing to replace the original sheath.

Does the tach twitch when you crank the engine? The ECU will not power up
the fuel pump unless it detects ignition pulses.

 

Tach does twitch.

Has spark (I believe but not 100% verified).

Cannot hear pump noise.

When it dies, it's like someone threw a switch.

thanks

jimB

 

Can you measure voltage at the pump? Did you replace or resolder the relay
already? Fuses ok?


When mine suffered the harness failure it would randomly start running
poorly and have no power, then recover. Then one day the engine just shut
off and would not restart. When I cut open the harness to replace the wires,
I was shocked it had run at all, the insulation literally crumbled to dust
from a large bundle of fuel and ignition system wires a couple feet long.

 

Hi Folks...

Look at the date stamp on the relay...if it's close to the manufacture
date of the car replace the relay...it's all of $50 for good quality/
OE and $30 for Chinese. It is not worth the hassle to resolder the
joints, etc. unless you a truly a geek.

Best regards

wharf rat

volvos since 1969 PV544, 122 Amazon, 145, multiple 240's, 940 and,
currently, 87 245 and 93 850.

 

In a time long ago and a galaxy far away, jimB did his own car
repairs. No longer. Well, some repairs anyway...

With the help of a Bosch ignition guru <read:geek>, problem was
determined to be Hall Effect Sensor in the distributor. Power module
was also bad but I don't know how that figured in the cause/effect
equation.

I have a parts car (doesn't everyone?) and I pulled the computer,
distributor and power module.

All betta

Second benefit, speedo works now (intermittant before). Go figure. Did
pull/replace grounds at computer bracket.

Had it been the harness, car would be in the scrap yard by now.

Not that it's terribly relevent, but, I do still have a 1987 harness
from the parts car. Is that one the type that doesn't rot?

jimB

 

No, that one rots too, but for about 30 bucks in parts and a couple hours of
labor and you can rebuild it like new with new wires, or you can buy a nice
used harness from Dave Barton for a couple hundred bucks. Installing it on
the car takes about an hour. You'd seriously scrap the car rather than do
that?

 

Well, I suppose if it only takes an hour, that WOULD be silly. Who
knew.

I will keep it in mind.

I would have to go with a new or reliable used harness. Me and
soldering irons don't get along.

I am actually a professional designer. I have designed and built
harnesses from scratch but never tried to splice into one.

I had someone splice a harness (from a u-pick) for me on a car that
had had a fire. Didn't work too well.

It ended up adding a lot of failure points.

If this is such a problem, maybe I should build a harness board and
sell harnesses <grin>.


jimB

 

It wouldn't hurt, up until around '89 they all fail, it was an experiment in
biodegradeable insulation, however engine heat and oil caused it to degrade
much more quickly. Given more time and a source of new connectors, I'd have
built a whole new harness myself. Brand new ones are obscenely expensive.

When I did my '87 I had little choice, the car died and I needed
transportation so I bought a few rolls of wire and a big pile of heatshrink
tubing. Removed the harness from the engine but left it poking through the
firewall and proceeded to replace each wire from near the firewall to right
at the connectors. The copper was oxidized in some places but I was able to
scrape it clean and solder a new wire on then slip a piece of heatshrink
tubing over it. The job took about 4 hours and I had to do it on the street
because I couldn't get the car up my steep driveway, it was miserably cold
and raining out, but the finished product looks factory and the car has been
dependable ever since.

I also built a custom harness when I put Megasquirt on my 242, that one I
took my time, salvaged connectors from the scrapyard and built the whole
thing from scratch. Took longer but it also looks factory original and has
been dependable.