Hey all,

today my wife left home, stopped at a

friend's house (cut engine off), then started

it again and was driving down the highway when it

all went dead. Upon attempting to restart it won't fire.

;she calls me at work and I run out and start doing

the usual, twisting all of the glass fuses to make

sure that no corrosion is preventing starting. I then

remember about the fuel pump relay. I've been contemplating

doing a resolder job on another car's OD relay, now I had to

'think about this one.

I'm kind of in a remote area and I need to get the car going.

So this is what I did, I took the cover off of what I believe is

the fuel relay as it's the only relay thing I see under the dash

by the drivers knees. I take the cap off and see the circuit board.

It smells normal, I don't see any cracks, I do see brownish flux on

the contacts that connect directly to the posts that protrude from the

relay, I re-metled these connections hoping that it'll re-connect the

connections. I will now re-check my under hood connections and make

sure I don't have a bunch of corrosion and I'll re-check the fuses

which are glass.

Any advice would help.

Josh,

with all the acessesories off, turn the key to to "on" position without cranking it. You should hear a click and about a second of fuel pump sounds then another click of it shuting off. Sometimes you don't hear the first click bacause it happens at the same time you are turning the key. You should always hear the second one. If not, the relay Dan showed us, on the left, is the bad boy. Easy to get at. I just had to buy one Saturday, $34 I think. For my 91' 240 with 130K miles.

Fuse #6 supplies the juice. Check for melting. See my post from this morning: "Fuse holder #6 melting"

Steve M.

Josh --

Your fuel pump relay is mounted to the inside firewall, passemger's side, just above the fgelt kickpad. A tall pasenger's feet might kick it.

In a pinch, you can push into the solder cracks (assuming you have some and can see 'em with a magnifying glass) using a sharp object, such as an awl or thumb tack. This will deform the soft solder and "stake" the connections together. They may work again for a few hours ot few days.

Resoldering is best, even if the connections are now OK.

In the pix below, the fuel pump relay is on the left. (OD is on the right.)

Don Foster (near Cape Cod, MA)

Don,

Thanks for the reply. My fuel pump relay looks smaller in my 92, I ssem to remember you posting a close-up of the circuit side with the soldering re-done. I am right in assuming that I should just lay a bead of solder over all joining connections? Just add a whole layer of solder to it all, avoiding, of course, cross-connecting...

My problem turned out to be fuse number 6. I really couldn't tell that it was dead, it looked normal. Next time I will change it first no matter what, as well as premptively re-solder the OD and fuel-relay.

Here is a question-why is fuse six giving me such a hard time? Should I change the fuel filter? Is too much juice being used to suck fuel through it?

Thanks for the help.

In my opinion, your best solution would be to desolder the relay board completely, then resolder it. The factory soldering is plagued by a combination of cheap solder and poor manufacturing process.

Use either a vacuum-style soldersucker or a desoldering wick. Since there is quite a bit of solder the soldersucker would be the preferred choice. You could be there all day using the wick, and you would run the risk of overheating the traces and causing them to lift. The good thing is the board is good quality (like FR-4) and they can take quite a bit of abuse, unlike the PCBs on some cheap Japanese stereos I've 'fixed' =8o

When you are done, the solder should be nice and shiny, not the dull grey they used to be, and should taper upward to a point. If it's all round and looks like a blob of mercury, you've got too much solder. Don't just 'lay a bead of solder' - geez, are you going to use a caulking gun or what???

Of course you could always 'buy' a new relay, but what's the fun in that?

Josh,

Highways, parking lots, drive way, alongside gas pumps, it doesn't matter, I've done them all. Sounds like you had a failure of the glass tube fuse type. Sometimes the element fails at the ends, hidden out of view by the metal jackets at the ends rather then in the middle where the element is narrow and in view. Inserting a spare fuse is a good way to check this - and listen for the sounds of the fuel pump.

Next step is to clean fuse block connections for corrosion.

Michael ('83 245GLT, '83 240DL, '92 240DL, '90 760GLT)

Josh --

"...just lay a bead of solder over all joining connections? Just add a whole layer of solder to it all, avoiding, of course, cross-connecting..."

Not quite. That would result in what's usually called a "cold solder joint," where the solder beads up over the actual electrical connection but doesn't penetrate the connection.

You want to heat the existing solder so it melts and reflows, and at the same time add new solder. You add new solder for two reasons.

First, the new solder will include rosin (or "flux"). As the flux melts, it cleans the oxide from the connections, permitting proper joining of the metals. Also, the flux lowers the surface tension so the new solder will flow into the electrical connection rather than beading up around it.

Second, new solder has a different and better mixture of metals, so it forms a much stronger union than the solder used in the automated process.

"...why is fuse six giving me such a hard time?"

Is this the first failure for that fuse? Maybe it's the wrong value, or maybe the stupid thing simply broke from road vibration. It happens.

Don Foster (near Cape Cod, MA)