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Sorry in advance for the length of this post. I have had a series of very strange and possibly related fuel pump and charging system problems over the last 2-3 weeks that I could use some help with. My car is a 1987 240 wagon with automatic transmission. A couple of months ago I noticed the main fuel pump was making more noise than usual and the car would stall after driving at speed then getting into stop and go traffic. I suspected the stalling was related to the pump noise so I replaced the following items (in order) to try and fix the stalling:
Fuel filter
Fuel pump relay (replaced with used)
New 25 amp fuse at battery
In tank pump
Main pump
None of these fixed the main pump noise, but I did find that the tank pump was bad, and after replacement the car stalled out less frequently.
I drove the car a few days with the noise still present, then noticed my battery didnt appear to be charging. I was getting 11.5-12 volts at the battery so I suspected a bad alternator since I have replaced the alternator 4 times over the last year. The alternator had a lifetime warranty so I took it back and they gave me a new one with out testing it. The new alternator also failed to charge the system. The symptoms were as follows:
D+ voltage with key on = 1.5 volts (replaced wire to firewall just in case)
Voltage at B+ = 12v with key on, 12.0-12.5v with car running
Voltage at battery + post with car running = 12.0-12.5v (no appreciable drop from B+ so cable is OK)
New ground strap on the alternator
The battery light comes, as well as other dash bulbs when the key is on, but no battery light when the car is running, even though it only puts out 12+ volts.
Swapped battery with a known good one, no effect on voltage
Checked with 2 different meters, same readings
Took replacement alternator back and had it bench tested. It put out 15v so I think it is OK.
At his point I started suspecting the fuel pump noise and the charging were related. On a whim I pulled out the new/used pump relay and re-installed the original and the voltage magically jumped to 14.5 volts at the battery. With that problem solved I went about addressing the fuel pump noise again. It took a few more days of dead ends but I finally determined the fuel pressure regulator was bad and replaced it, which fixed the pump noise and the stalling problems. Life was good until the next day when I noticed my dash lights were dim and checked voltage to find the charging problem had re-appeared. The symptoms are identical to before. I still suspect something with the fuel pump electrical feed is the cause so I have concentrated on checking it out. I have taken the following readings/observations:
In tank pump has battery voltage at the pump and pulls 2 amps.
Main pump has battery voltage at the pump and pulls 4 amps
Jumpered direct from battery to both pumps and current remains the same.
Have swapped the relay back to the new/used one no impact on charging
Pulled all fuses except main and tank pump no impact on charging
Pulled tank pump fuse while car is running no impact on charging
Pulled main pump power plug while running voltage jumps up to 14v for a second or 2, then car dies from lack of fuel.
The last observation makes me think the main pump is somehow causing a large load on the system and drawing down the voltage (I am not a electrically inclined so I dont know if this is possible). The pump came from Advance Auto and was smaller in diameter than the original pump. Is it possible that running the pump with the bad regulator for a few days damaged it and is causing this problem? How about the relay? Is there a way to check it to see if it could be the cause? I am really tired of buying parts that dont fix the problem so any guidance on what to check before I sink some more funds into this car would be greatly appreciated.
Thanks
Bart
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