In another thread I made I was told I needed to replace my fuel pump soon, and it's really starting to show it. It hasn't blown any more fuses but the other day when I started to go it started sputtering constantly, and barely gave me enough power to get off the road. I moved the exterior fuel pump a bit and after trying it she magically started right back up and let me get home. I haven't had that problem since because I've been keeping it over a half a tank, but now it occasionally feels like I'm not getting enough fuel and it drives slower.

I know I have to replace the exterior fuel pump, but my question is do I have to replace both of them? I don't know for sure if the in tank one is working properly, but if I don't have to replace it I'd rather not. And speaking of the in tank pump when I was taking a look at it it seems the previous owners wired in an extra wire to something (I can't see where it connects because the filler tube is in the way) and the wire goes all the way under the car into the engine bay but isn't connected to anything. Has anyone else ever heard of this type of thing, and if so what is the purpose?

Some smaller concerns is that my reverse lights have never worked. I checked all the fuses and they're fine, but the fuse box is pretty rusty which leaves me to believe some things aren't functioning. For one I've never seen my front cooling fan work, my cruise control doesn't work (but I don't how to work it anyway, I'm pretty sure you hold the button but it doesn't set even when it's on), my rear wiper doesn't work, and like I said my reverse lights don't work. If these each have their own solutions I'd love to get some advice, but if it's the fuse boxes fault is there anything I could do other than somehow getting another fuse box from the junkyard (which I can imagine would be a real pain to remove and reinstall).

 

I would clean up the fuse box first. Disconnect the negative battery cable. Remove all the fuses, paying attention to which goes where. Take a Dremel or, by hand, use a BRASS brush and brush the rust away from the fuse box. I would replace any fuse that looks suspect. After cleaning spray a little electrical contact cleaner. CRC is one brand. When replacing the fuses use a little dab of dielectric grease (tune-up grease). Permatex makes it. You may have to bend the fuse terminals slightly to get good connections with the fuses.

 

Thanks, I'll have to try that, would be nice to get those things working finally.

Any advice on the fuel pump issue? It's semi working for now but it would be nice to have the knowledge asap so when it does go I'll know what to do. This is my daily, and my parents need their vehicles, so I can't afford to be dicking around with it for a few days when I need to get to college.

 

Are you sure it's a fuel pump issue? Mine turned out to be failing Hall sensor and bare wires on the Hall plug.

 

Forgive me for my ignorance but I have no idea what that is, whereabouts would this be located?

I'm not 100% that it's my fuel pump but I was told that the fuel pump was going to become an issue after it blew a fuse. And when it was sputtering I checked everything I possibly could, but moving the fuel pump around somehow made it work.

Reminds me of a story someone told me about their Chevy 1500. The fuel pump was going but you had to take the bed off to get to it, so when it didn't work he'd just go under the truck and bang on the tank with a hammer and it would work, lol.

 

Sounds like it's the fuel pump... I've heard you can stick some hose down the gas filler hose and you should hear a buzzing noise being the pre-pump. Or you could just listen to the main pump for excessive noise. IMO I think it's the pre-pump, they've been known to be the culprit of fuel starvation and it sounds like that's what you're experiencing.

 

i will share my experience with my dual pump '87 744ti. I figured since i was upgrading i'd replace both pumps just to be safe, as well as the "sock/strainer" attached to the transfer pump (in-tank pump nomenclature). Good thing i did because it was nasty and falling apart! Anyway afterwards i couldnt hear the damn thing kick on with the key flipped to "on". But i was getting decent voltage and if i applied direct voltage from the battery terminal to the red wire on the pump harness going into the tank (at the tank) then i could feel the tank vibrate much more.

Hence my reasoning to upgrade the friggin fuel pump wiring with 14 gauge wiring and use relays and 20A fuses. run the wiring from the + on the battery to one side of the relay, then to the fuel pump, then cut the original fuel pump wire close to the pump and use that to signal the relay to switch. i'd also do the same for the main pump.

FUEL PUMP OUTPUT DEPENDS ON AVAILABLE VOLTAGE AT THE PUMP!!!!

Therefore given that our cars are turbo, it would be very prudent to do this. I learned the mod a long time ago on my awd turbo talon, its a great, cheap, and simple modification that only takes an hour, tops and guarantees you're getting enough voltage to the pumps. it matters. my intank pump gets just over 13v now with stock wiring. i have 14.2v at the battery (using dave barton's adjustable voltage regulator). it makes enough of a difference to result in the aforementioned vibrations/noise from the pump itself.

 

The Hall sensor plug is on the bottom of the distributor. If the Hall sensor fails, you will get no spark. Lots of times, before it fails, the engine may hiccup and fail to start at times. Go to www.stepbystepvolvo.com for free guide to 740 no-starts.

 

So that's probably what that wire going to the engine bay from the in-tank is, but it's not hooked up to anything. On a related note I also found a red and green wire that end in the fuse box area and go under the passengers side carpet and both have fuses on them, but I don't know where they go from there. It could be possible that it already has the modification but it's not hooked up, but then why would it end in the fuse box area. I'm going to have to do a lot of looking around the car, those rednecks (and whoever else owned it) did some funky *** wiring to it, I even have a car phone hook up (which is why I have that radio signal amplifier).

Thanks for the advice though, I'll definitely have to do that when I end up changing them.

 

The really easy way to check for function of the in tank pump is to disconnect the pressure pump under the car, get your head under the fuel tank and have someone turn teh key to ignition. The pump will run for 2 seconds if it is good.
The fact you have running issues below a half tank of fuel tells me you have an in tank fuel pump or fuel pickup problem. I would check the fuses first. With blade fuses, you can use a test lamp to check for voltage at the small exposed holes on top of the fuses. Earth alligator clip to body and probe fuel pump fuses both sides to check for power with ignition on. If this is O.K, I would just go ahead and order a new in tank pump, they cause lots of issues when they are old and are the cheaper pump to replace.
All the in tank pump does is lift fuel and provide it at a slight pressure to the pressure pump under the floor of the car. Running voltage is irrelevant if the fuel regulator is bleeding pressure and returning fuel to the tank, it means more than enough pressure and fuel is being delivered.

Regards, Andrew.