volvo voo-doo doo-doo

whale · Post by **whale** » 24 May 2004, 00:08

Well I hope someone finds the title of this topic to be of enough interest to read and maybe even be able to clue me in on a diagnostic nightmare.

We live on a small island with not a lot of resources especially when it comes to things swedish - the car is not running and when i called a guy who claims to specialize in foreign -exotic - cars he said he dosn't like cars that don't run and so don't tow yours in!...and so it goes...

Anyway we have a normally very sweet 93 940 non-turbo. A few months back, just short of 100K I replaced everything I could think of: plugs,rotor,cap,wires,battery,tires,belts(including timing),hoses,drained fluids,aircleaner,fuel filter,cleaned flametrap and cleaned out throttle body and pretty much went through things.

All was great for about 4000 miles then one night my wife calls and says the car just died on her and so began the nightmare.

Getting it home in the rainstorm was a piece of cake compared to not being able to figure out the why.

After a while I discovered the following: when I pull fuse number 11 for one of the fuel pumps, it will start but run poorly. And that is it - I am stumped and I just hope someone can maybe clue me in to what possible relay or some such is messed up - all parts have to be ordered off island and waited for for many days before they show up - so thanks to anyone who reads this...

Volvord · Post by **Volvord** » 24 May 2004, 10:05

Interesting problem.
If it will help I have the wiring diagrams for your car that I could send to you, PM me your email address and I will send them.

Post by **matthew1** » 24 May 2004, 11:40

Little reminder for the Volvo owners here...

This link to wiring diagrams for 850, 960 and 740s can be found on my main page.

LaRy · Post by **LaRy** » 24 May 2004, 11:49

I do not believe in voo-doo- doo -doo, but I believe in bad grounding! You have lost the real ground somewhere, probably for the fule pump, ma

Guest · Post by **Guest** » 24 May 2004, 11:49

Your offer is very generous but I am wondering how exactly this
might help isolate the problem? There is some weird (to me) relay or
switch or somesuch that seems to be the culprit - when we get the
thing running by removing the pump's electric juice, the engine is
strong sounding and no smoke or other obvious malfunction - it just
won't drive or run with the fuse re-connected.

Anyway this is not looking a horse in the mouth syndrome - just a
confused guy

Volvord · Post by **Volvord** » 24 May 2004, 12:18

Usually when a situation like this happens (removing a fuse to make something work) it is the result of a bad ground which causes a feedback loop.

My tracing the wiring it may help identify the source of the trouble and the locations of the grounds. It will also identify the relays which control the circuit and identify their locations.

Guest · Post by **Guest** » 24 May 2004, 13:04

If you, or a friend, can solder, try pulling the fuel pump relay, open it up, and resolder the printed circuit board inside. I did this to my '93 940 as soon as I got it. Good PM anyway.

I had a no-start intermittant on the 940. That turned out to be bad insulation on the cable to the crank position sensor. The cable to the sensor was split right at the poinr where it goes into the sensor. This is down on the bell housing behind the engine. You might try feeling this cable to see if it feels like split rubber on it. Many recommend that this sensor be replaced at about 100K miles. However, the fuse 11 thing is a puzzle.

LaRy · Post by **LaRy** » 24 May 2004, 13:21

By a quick check of the wiring diagrams I would definitely check the following grounding rails and connections in following order:
Ground connector in load area
Ground connector at left tail lamp
Ground connector in fotwell at right A-post.

Look for corroded connections and loose amp connector and also that the ground rail itself also has a good connection through the fastening bolt.

spook · Post by **spook** » 24 May 2004, 17:14

Dear whale,

Good p.m. and may this find you whale (well, in a southern accent)!

Unless I'm mistaken, re-soldering a relay means ensuring that each component has full contact with the board. In some cases, the gaps are too small to be seen with the naked eye, but are still large enough to disrupt the power flow, and so create problems.

Therefore, touch the (pointed) tip of a soldering iron to the bottom of the connector's "leg", where it sticks through the circuit board.

Plainly, one has to be precise. One should not to allow solder to flow too freely.

This is still a low-risk, high-return task. If you fix it, you've saved a pile of money. If you don't succeed, you're no worse off than you were.

If you need new relays, contact www.fcpgroton.com.

Hope this helps.

Yours faithfully,

spook

Don Foster · Post by **Don Foster** » 24 May 2004, 17:15

A classic problem with all things Bosch (and sometimes Hella, too) is failing solder connections.

My wife was stranded one evening with a bad fuel pump relay -- resoldering put it into first class condiditon, even better than new.

Two weeks later, same problem. But this time it was a flaky radio suppression relay (which is underhood in our '91 740).

Moral of the story: Resolder every relay in sight.

While this might not solve your problem, it's free and easy to do and stands a good chance of helping.

--
Don Foster (near Cape Cod, MA)