Stoner Dude Posted September 16, 2014 Share Posted September 16, 2014 Ok, here goes.......I have a 84 GL Station Wagon with a shady fuel pump. I have (2) in line see-through type fuel filters. The fuel filter that is located just before the carburetor is bone dry, the filter that is located between the gas tank and the fuel pump was full of fuel. I poured gas into the throat of the carb and it fired right up and ran for a few seconds then dies. The car has been sitting for a while but I always go out and start it ever so often to keep the battery alive. It hasn't been sitting so long that the gas has turned to varnish and i added the gas saver additive the last time i put fuel in it. I used my "hunch style trouble shooting technique" and determined the fuel pump went out. I bought and replace the fuel pump. In the process of replacing the pump i did notice when i took off the fuel line coming from the fuel tank that fuel was running out of this line so i had to plug it. (rules out a clogged tank). So with the new fuel pump and fuel pump filter installed i primed it at the carb and fired it up and it ran for a bit and died. I did this a couple times and then looked at the new fuel filter between the tank and pump and it was bone dry still. No fuel was going from the tank to the pump. So now im thinking the new pump is not getting power. The repair manual has zero info about where or if the fuel pump has a fuse or relay switch. If it does i don't know where it is. I have also been researching about the cut off relay switch. Does anyone know if there is a fuse and/or relay for the fuel pump and where that would be located??? Thanks for any help that can be offered Link to comment Share on other sites More sharing options...
BirdMobile Posted September 16, 2014 Share Posted September 16, 2014 (edited) There is a "module" (sometimes referred to as a "revolutions sensor") that runs the fuel pump. It is an approx. 2-1/2" square black box with a 6-pin connector, usually located under the left side of the instrument cluster bolted to the sidewall. I have also seen them (on older cars) bolted under the right side of the instrument panel. To diagnose, find a wiring diagram, and jumper the "keyed" power past the module to the fuel pump power wire. If faulty, you can [a] replace module, or jumper past module and risk death by fiery inferno as your fuel pump keeps pumping gasoline into your wrecked front-end. I personally chose , you just can't worry about everything! Edited September 16, 2014 by BirdMobile Link to comment Share on other sites More sharing options...
BirdMobile Posted September 16, 2014 Share Posted September 16, 2014 P.S. Search this forum, the module and wiring is well documented in at least one thread. Link to comment Share on other sites More sharing options...
Stoner Dude Posted September 16, 2014 Author Share Posted September 16, 2014 thanks for the input BirdMobile, lol. Gave me a good laugh there with the whole burning engine comment. I have seen that infamous module box and i was hoping i wasn't going to have to screw with it because of the contorted angle i will have to make my back in order to access it. Might be easier to just replace the whole car and move on down the road. But since im broke i'll have to screw with that module deal. Is that module dohicky availble at part stores? Link to comment Share on other sites More sharing options...
BirdMobile Posted September 16, 2014 Share Posted September 16, 2014 No, not available at part stores. It's a junkyard or Ebay only situation. I found one for $75 a few months ago after a brief search, which is why I decided to wire past it instead. Link to comment Share on other sites More sharing options...
BirdMobile Posted September 16, 2014 Share Posted September 16, 2014 The other thing you could try is running a new ground wire off your fuel pump to any nearby bolt or screw, using a ring terminal. Sometimes fuel pump problems are simply a glitchy ground wire. Link to comment Share on other sites More sharing options...
Stoner Dude Posted September 17, 2014 Author Share Posted September 17, 2014 (edited) Is this how you are thinking? One wire is all black and one wire is black with a white stripe. I want to spice into the all black wire correct? Thanks, Edited September 17, 2014 by Stoner Dude Link to comment Share on other sites More sharing options...
BirdMobile Posted September 17, 2014 Share Posted September 17, 2014 Yep. That's the overall plan. 1 Link to comment Share on other sites More sharing options...
rdweninger Posted September 17, 2014 Share Posted September 17, 2014 Dinky, get down to OK before this guy scraps an '84 wagon for no good reason. Got fuel ? Link to comment Share on other sites More sharing options...
Stoner Dude Posted September 19, 2014 Author Share Posted September 19, 2014 its looking more and more like the Fuel Pump Control Unit (FPCU) is bad. I tested the feed wires at the fuel pump and was not getting any power with the key in any position. I took the FPCU off and tested the hot wires and they worked as indicated in the below diagram. Is there another way i can further test the FPCU to know for sure Link to comment Share on other sites More sharing options...
Stoner Dude Posted September 19, 2014 Author Share Posted September 19, 2014 rdweninger it's got at least 3 gallons in it. 1.5 gallons the first time i started to fix it a month or so ago and another 1.5 gallons that i just put in there a couple days ago. Link to comment Share on other sites More sharing options...
BirdMobile Posted September 19, 2014 Share Posted September 19, 2014 (edited) First, add another 2 gallons of fuel, just to eliminate that as a possible cause. Second, you will NOT see voltage at the fuel pump with the key turned to the "on" or to the "running on" position. You need to actually have the engine running (providing distributor/coil pulses to the module) before the module will send voltage to the pump. I think there is something like 3 or 4 seconds of power sent to the pump when you first turn the key to the starter position, but it's not long enough to run to the meter and check for it, unless you have LOOONG test leads and put the meter in the cab with you, or have someone else turn the key. To test the module, simply pull it and jumper past it on the wire harness - run a wire from the "key on" power wire (Blue wire) to the fuel pump power wire (Blue/Red wire). If the car runs fine, you know it's the module that's bad. You can keep it wired that way for the "fiery death" option, if you want to roll the dice. Edited September 19, 2014 by BirdMobile 1 Link to comment Share on other sites More sharing options...
Stoner Dude Posted September 19, 2014 Author Share Posted September 19, 2014 I had my kid work the key while i used a tester light on the feed at the pump. Tried it a bunch and never got the light to come on. If i want to drive around a while with the jumper wire version, do i need to jumper wire the other circuits that are in this harness? What about the BLK wire on the supply side? Link to comment Share on other sites More sharing options...
BirdMobile Posted September 19, 2014 Share Posted September 19, 2014 (edited) On mine (1987 GL) I didn't have to jumper any black wires... but my fuel pump had it's own ring terminal ground like we discussed earlier in this thread, so the pump is grounded through that. If you don't run a separate ground, you MIGHT need to jumper a ground across the connector, if both legs of the fuel pump are wired to the connector (with your model/year, I don't know). You DEFINITELY need to also jumper the automatic choke wire to keyed power, as you indicated on your drawing, or your choke will never open and it will run crappy. I would try jumpering the keyed power and fuel pump power and automatic choke wires together, see if you are reading 12V or so between the 2 fuel pump connector pins with key turned on to the running position. If not, investigate the ground wiring further and either run a 2nd ground with ring terminal, or jumper ground wires at the module connector. Edited September 19, 2014 by BirdMobile Link to comment Share on other sites More sharing options...
Stoner Dude Posted August 9, 2015 Author Share Posted August 9, 2015 got an update on this. got the fuel pump working and now it appears my gas tank is clogged. I even tried to blow compressed air back into the tank (gas cap off) via the fuel line and I got no gurgle noises. Any body have an idea of how to unclog the gas tank? Link to comment Share on other sites More sharing options...
colemanapp Posted August 9, 2015 Share Posted August 9, 2015 pull tank, fill with gravel, shake, empty, rinse tank. Also theres a little raised metal screen, kind of like a sock. Its probably all clogged up and you might as well use a long screw driver and remove it too. Link to comment Share on other sites More sharing options...
Stoner Dude Posted August 9, 2015 Author Share Posted August 9, 2015 dang, i was hoping i wasn't gonna have to pull the tank. what is weird is it worked fine like a month ago. what could be clogging it up so bad? rust or something? Link to comment Share on other sites More sharing options...
Stoner Dude Posted August 9, 2015 Author Share Posted August 9, 2015 to removed the screen, do i get at it from the fuel line or the top where the sending unit is placed? Link to comment Share on other sites More sharing options...
turfman454 Posted August 9, 2015 Share Posted August 9, 2015 just went through the same thing. There is a drain on the bottom of the tank. I drained all the fuel out and then blew some air through both sides. ALso had a problem with a simple kink in the fuel line at the filter. There is no screen in the tank if im not mistaken. Link to comment Share on other sites More sharing options...
Stoner Dude Posted August 9, 2015 Author Share Posted August 9, 2015 turfman, what do you mean by both sides? Did it fix your clogged tank? Link to comment Share on other sites More sharing options...
turfman454 Posted August 9, 2015 Share Posted August 9, 2015 after unhooking the lines from the filter i used compressed air..35 psi to make sure the line coming from the tank was clear then i blew air from the fillert neck side to make sure it came out of the line going to the filter. It appears when i replaced the pump i kinked the line enough that it would gravity feed into the filter enough to make it crank and run a few minutes but the kink wouldnt let it fill up enough to keep it running. It doesnt take much to kink the line when you reaattach the pump bracket back into place with all the lines connected. The gas in my tank was 3 year ethanol and it had actually gelled up from sitting at my painters. Good luck it drove me nuts for awhile. Like you it ran fine until i replaced the pump. Its usually the simple stuff that causes problems and i was trying to overthink it Link to comment Share on other sites More sharing options...
turfman454 Posted August 12, 2015 Share Posted August 12, 2015 any updates Link to comment Share on other sites More sharing options...
Stoner Dude Posted August 12, 2015 Author Share Posted August 12, 2015 nothing yet, it's been too hot to screw with. I'm gonna try and get out there early this weekend. Link to comment Share on other sites More sharing options...
Stoner Dude Posted August 17, 2015 Author Share Posted August 17, 2015 took the rubber hose off that goes from the tank to the fuel pump, no gas came out. I went ahead and drained the gas tank via the drain screw. it had about 6 or 7 gallons of gas in it. I took the fuel sending unit off and looked inside the tank and noticed the metal gas tube has a little filter on it, see picture. Not sure if the filter is clogged or what. Is there a way to gain access to the inside of the tank? I am prepared to pull the tank and see if there is an access hole on the top?? Link to comment Share on other sites More sharing options...
colemanapp Posted August 17, 2015 Share Posted August 17, 2015 Theres an access point to look inside tank after you remove the fuel level sensor. Its got a rubbery gasket that's... well, be careful. Pretty sure its on the back of the tank. You can see the 'sock' once you remove that. Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now