Drummer Posted October 9, 2015 Report Share Posted October 9, 2015 This is on my 93 Cutlass convertible with the 3.4. Ive been chasing a fueling issue for the whole summer and im not sure what to think is going on. When i start my car when it's cold i have fuel presure but as the car warms up and cycles the fan a couple times the fuel gets air bubbles mixed in with it and eventually is replaced with nothing but air. If i let it sit overnight and cycle the pump a couple times i get fuel pressure but once the car warms up again the same thing happens. And the car runs horribly for the first couple minutes as i have to constantly play with the throttle to keep it running and eventually it will idle but if i step on the gas the motor bogs down then revs up So far I've replaced some vacuum hoses, fuel pressure regulator, ohmed the injectors(12.2-12.4 ohms)changed the fuel filter, spark plugs and wires (since I had the upper intake off). The only other thing I can think of is my fuel pump is on its way out, but i can hear it priming so I'm assuming it's running. I just went and bought a fuel pressure gauge so tomorrow ill see if the pressure bleeds off or not as it runs. Is there anything else that could cause these -symptoms? Quote Link to comment Share on other sites More sharing options...
Imp558 Posted October 9, 2015 Report Share Posted October 9, 2015 Has to be the fuel pump crapping out. If you get the fuel pressure gauge from harbor freight be very careful that little thing in the fitting doesn't fall out, it depresses the button in the schrader valve. I have 2 of those gauges that don't work because that thing is missing. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted October 9, 2015 Report Share Posted October 9, 2015 i can't see this happening any other way. somehow, the pump is pulling air instead of fuel, perhaps cavitating once it heats up? Quote Link to comment Share on other sites More sharing options...
Drummer Posted October 9, 2015 Author Report Share Posted October 9, 2015 What would be a good sending unit to get? Spectra, Dorman, or Delphi? Quote Link to comment Share on other sites More sharing options...
rich_e777 Posted October 9, 2015 Report Share Posted October 9, 2015 Delphi is the OE part, I`d go with that unless the Dorman has the only lifetime warranty. Quote Link to comment Share on other sites More sharing options...
Imp558 Posted October 9, 2015 Report Share Posted October 9, 2015 Maybe order straps too, unless yours are in really nice shape Quote Link to comment Share on other sites More sharing options...
Drummer Posted October 9, 2015 Author Report Share Posted October 9, 2015 The car was from florida so the underside is clean. I might take some pictures lol. Quote Link to comment Share on other sites More sharing options...
Drummer Posted October 9, 2015 Author Report Share Posted October 9, 2015 Ok so the cheapest Delphi I've been able to find is 170 shipped from Rock Auto. Summit wants 214 shipped for it. Quote Link to comment Share on other sites More sharing options...
Imp558 Posted October 9, 2015 Report Share Posted October 9, 2015 that sounds a little high I've been pricing race pumps around $100, OE equivalent replacements are like half that on RockAuto Quote Link to comment Share on other sites More sharing options...
Drummer Posted October 9, 2015 Author Report Share Posted October 9, 2015 I should have specified that it's the whole sending unit. Quote Link to comment Share on other sites More sharing options...
Imp558 Posted October 9, 2015 Report Share Posted October 9, 2015 oh that is pretty good Quote Link to comment Share on other sites More sharing options...
Drummer Posted October 14, 2015 Author Report Share Posted October 14, 2015 Drained my gas tank last night. It took 4-5 hours to empty 6 gallons but at least it was able to. Hopefully after work I can drop and reinstall the tank before it gets too dark. Quote Link to comment Share on other sites More sharing options...
Drummer Posted October 15, 2015 Author Report Share Posted October 15, 2015 Is there any way to test the fuel level sensor? My tank is completely empty but my gauge is reading 1/8th tank. Quote Link to comment Share on other sites More sharing options...
Imp558 Posted October 15, 2015 Report Share Posted October 15, 2015 See if the arm might be bent too straight, the float might be hitting the bottom too early. If I'm not mistaken our senders are 0-90 ohms. Perhaps someone can confirm they used 0-90 in 1993. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted October 16, 2015 Report Share Posted October 16, 2015 0-90 is accurate. Goldenregal 1 Quote Link to comment Share on other sites More sharing options...
Drummer Posted October 16, 2015 Author Report Share Posted October 16, 2015 Should I reuse the pump pulsator dampener? The replacement pump just has a hose with 2 hose clamps to go in place of it. Edit: It seems like newer designed pumps don't use it so I guess I don't need it. Heck it could have been the problem with my old pump. Will test to see if it holds pressure or not. Quote Link to comment Share on other sites More sharing options...
Garrett Powered Posted October 17, 2015 Report Share Posted October 17, 2015 How can you tell it has air bubbles? it hisses at the valve? I am chasing a fuel problem on my 88. sounds like the symptoms are similar, but one thing I noticed the other day was the relay was getting super hot every time it acts up. Quote Link to comment Share on other sites More sharing options...
Schurkey Posted October 18, 2015 Report Share Posted October 18, 2015 How can you tell it has air bubbles? it hisses at the valve? I am chasing a fuel problem on my 88. sounds like the symptoms are similar, but one thing I noticed the other day was the relay was getting super hot every time it acts up. First Guess: Pump drawing far too much current, causes relay contacts to overheat. Second Guess: Burnt relay contacts cause excess resistance, which creates more heat. The pump starves for power while the relay becomes a space-heater. Either way, the pump is probably ruined, as is the relay. If that were in my driveway, I'd test the fuel pump with (at minimum) an ammeter to determine current draw, and a fuel pressure gauge. Better still would be the fuel pressure gauge and an amperage probe connected to an oscilloscope, so you can read pump RPM, current draw, and look for defective armature bars on the electric motor that powers the in-tank fuel pump. If you don't have those tools...you're probably just going to have to replace the pump and the relay, inspect the wire harness INCLUDING the harness in the tank which is a VERY common failure item, and hope for the best. The in-tank wire harness is about twenty dollars, I'd strongly recommend it--it's uncommon to see an in-tank harness that isn't ruined by corrosion. Don't forget the fuel filter, and the fuel pump inlet "sock", too. Quote Link to comment Share on other sites More sharing options...
Garrett Powered Posted October 18, 2015 Report Share Posted October 18, 2015 I'm going to take on the project in that type of attitude. Just go through all the wiring and redo it. I had dropped the tank a few years ago before I tuned out some of the engine surging by tweaking the throttle follower table, and the resistance problem with the fuel pump wire started there and but I was able to get by driving it till now. the wires in the tank looked fine, but I am saying fuck it and run a thicker wire all the way back, and may as well like you say put a new pump and relay. probably will buy a new sender and throw it in there too. Might as well, Grampa, as I call it, deserves all the love. I am about to rebuild the motor with a cam and bolt on an intercooled GT2871r, so it will be needing the fuel system straight. I am also going to get the alternator rebuilt somewhere at a shop and drop it back on all fresh and test it at Idle Quote Link to comment Share on other sites More sharing options...
Drummer Posted October 19, 2015 Author Report Share Posted October 19, 2015 How can you tell it has air bubbles? it hisses at the valve? I am chasing a fuel problem on my 88. sounds like the symptoms are similar, but one thing I noticed the other day was the relay was getting super hot every time it acts up. Yes it would hiss very little air along with fuel, and gradually get worse to the point of just tons of air. I also noticed when i was draining the fuel out of my tank that my pump was making different pitch tones that correlated to the amount of fuel that was coming out of the hose which was another indicator that my fuel pump was on its way out. Quote Link to comment Share on other sites More sharing options...
Drummer Posted October 20, 2015 Author Report Share Posted October 20, 2015 Well I reinstalled my tank with a new pump and she fired right up.......but now my sending unit isn't reading. Oh well that's another issue for next year. Quote Link to comment Share on other sites More sharing options...
Imp558 Posted October 20, 2015 Report Share Posted October 20, 2015 The arm is probably bound up. Quote Link to comment Share on other sites More sharing options...
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