Things are not always what they seem.
It started out with a ride on a flatbed, I was about 10 minutes from home, the car was running great when it suddenly ran rough, sputtered and then stalled. I glided over to the shoulder. It would not start, it just turned over quickly. I called for a flatbed and looked for answers on the boards while I waited..
As the car cooled, it started to catch when I tried to restart it. By the time I finally got it home it started up. This behavior seemed to tell me that I was getting gas and spark, and the issue was possibly with the enrichment circuit that adjusts the AF mixture as the car warms up, what we old timers might still refer to as the "choke". This is controlled by the temperature sensor which is located in the head for cylinder number 3. It is another "classic" problem spot, or that is what I gathered from reading. I took DCR measurements when I got home and they were low across the board. The sensor is a thermistor - a resistor that changes value based on its temperature. They can go open, high or low, so it was a reasonable failure mode for it to have. The car ran in my garage for 20 minutes and stalled as I measured the sensor. Low resistances would tend to run leaner.
I ordered a new temp sensor since my readings were off, I have a nice Fluke meter (so it wasn't that), and the car ran for a while before stalling again - so it had fuel & spark. I replaced the temp sensor (HERE), and when that didn't resolve the issue I replaced the coil (HERE). And by this time the car would not start at all. Wow, I am good at this stuff!
I don't have the special fitting (M12 x 1.5 Female) to let me check fuel pressure so I had not checked that. So I hot-wired the fuel pump from the battery + terminal to the fuel pump (low side of its fuse) to confirm it was working - and instead confirmed it was on death's door - it sounded like a bag of bolts falling down the stairs and started and stopped at random. I ordered a new fuel pump and the copper crush washers it uses.
Fuel Pump: 944-608-102-04
Copper Crush Washers: N-013-812-2. (12 x 15.5 x 1.5mm)
The fuel pump (Blue, this is the stock Bosch from 1988) is located under the belly pan that protects your front suspension and steering rack. 2x8mm hex head bolts and 2x17mm nuts + washers come off. Try to do it carefully so the sway bar doesn't move, I did it after the car was in the air and the suspension was at full droop. That worked out well when it was time to put it all back.
Basic steps:
Disconnect the battery's negative terminal. I put mine in a plastic bag to make sure it can't touch anything.
Ensure you have good ventilation, gloves, fire extinguisher, etc. Gas is not your friend.
Drain the fuel tank
Remove the old pump
Install the new pump
Put in a gallon of gas, and run the car looking for leaks.
If it's all good, put the belly pan back in place and put gas back into the tank.
Naturally I had recently filled the tank so I had to drain 20-ish gallons out first. I bought 3 new 5 gallon jugs. The Quickjack lifts the car enough that I could just let the fuel dump out. I clamped off the intake line, found a tube that would fit the hose and let me extend it into the jug and then removed the gas cap and loosened the clamp. It worked well and I had minimal spillage to deal with.
Here you can see (L to R) the cap, then a crush washer, the banjo fitting, the next washer and then the fitting for the no-return valve (the pump comes with the valve fitted already). You can also see the boots for the 2 electrical connections.
Using a 17mm and a 19mm crescent wrench, unscrew the top cap on the pump. Cap is 19, the 17 is for the valve body so you can stabilize it. You can see the banjo fitting in this picture as well as the mount and the rubber pad in the clamp that holds the pump.
The pump was filthy when it came out so I could not see the polarity markings. I used a brush and some brake cleaner to get through the dirt.
Now you can see the "+"on the left side here, just below the contact. On mine the + terminal was smaller (7mm vs 8mm for negative terminal) and in a pinch you could measure the DCR - negative side has a lower DCR to ground. I put Nyogel on the contacts before I put the boots back on the new pump. This should help keep them from corroding.
Here is the new pump in place, ready for testing. It worked fine and didn't leak so I got to put the car back together and go for a drive. I needed to use a small screwdriver to line up the holes for the skid plate bolts, but they were already very close.
Sources:
Copper Washer (12 X 15.5 X 1.5 mm) Part#: N-013-812-2-M30
Bosch Fuel Pump: 944-608-102-04
Special thanks to the Impact Bumpers BBS for the idea of just hot wiring the pump at the fuse panel. Sometimes you just get stuck working a problem, and this got me unstuck. :)
{I have since found a copy of the factory shop manual which includes hot-wiring this across the fuse panel, so I guess it is an "approved" tactic. }
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