derburger Posted March 9, 2009 Share Posted March 9, 2009 400 miles after I replaced my 86 XT's gas tank due to rust, I am having fuel delivery issues. The fuel pump is buzzing/vibrating loudly, the engine will stall after sitting at idle for a while, and will stumble upon acceleration. This is a new issue, 200 miles after replacing the gas tank it appeared, and I barely made the other 200 home; the XT stalled the minute I got off the highway, I was able to drive it home.... if I kept it above 2000 rpm. All of the fuel hoses are the proper size and fit, hose clamps are tight, I've tried 2 different fuel pumps and filters and there are still fuel delivery problems/ the fuel pump buzzing. Two causes of this issue I can think of are these; a supply hose is sucking air somewhere, or the fuel pressure regulator has gone bad. Do you think a faulty fuel pressure regulator can cause my fuel problems? I won't be in town to work on my XT for a week, so if I need to order parts I need to do it soon. What's a good place to buy a pressure regulator, if that's the likely cause of my fuel delivery problems? I think after solving this I can stop working on the XT every weekend and give my older MB some attention Link to comment Share on other sites More sharing options...
rpholz Posted March 9, 2009 Share Posted March 9, 2009 was the line between the tank and pump clear? did that line collapse possibly? was it completely fine until 200miles down the road? is there possibly bad gas in there? on a side note thanks for the advice on the hose clamps for my xt's tank. only time will tell if i come up with the same issues as you again. Link to comment Share on other sites More sharing options...
derburger Posted March 9, 2009 Author Share Posted March 9, 2009 bump Link to comment Share on other sites More sharing options...
rpholz Posted March 10, 2009 Share Posted March 10, 2009 could it be your fuel pump wiring is faulty? i had to rewire my xt. not sure if this is it but could be a place to check? Link to comment Share on other sites More sharing options...
john in KY Posted March 10, 2009 Share Posted March 10, 2009 Pull the fuel line at the pump that feeds the pump. Every time I have done this fuel flows freely. If you don't get a flow then there is a problem with the line between the pump and tank. Don't think replacing the FPR will do anything. Link to comment Share on other sites More sharing options...
derburger Posted March 15, 2009 Author Share Posted March 15, 2009 Bump, some more info... I rechecked all the fuel hoses again and they are tight with proper fitment, the supply hose under the tank was fine. I blew out the return line. The pump still makes noise, but I didn't feel any vibration or bubbles in the supply hose when the car was running. My next guess is that the fuel pump is bad. Although I put on my spare Loyale fuel pump and that one made noise too. When I pull of the supply line, lots of gas comes out, I don't think there's blockage in the tank. I'll try my spare Volvo FI fuel pump, which wasn't run on rusty gas by me, to see if there is the same issue. The car still idled high after I replaced the tank and pump, but the pump didn't make noise & stall the car until about 200 miles. Is there some sort of filter in the gas tank at the supply line? The tank is brand new "Spectra-Premium", I don't know how that could be fouled already. I know the fuel pump is for "pushing" fuel rather than sucking, so a supply issue would make sense for the noise, but I can't find any issue there. I looked at the little "sock" in the inlet side of the pump and didn't see anything in there, but I didn't attempt to clean it. I'll change out the fuel pump again tomorrow... Other guesses include clogged injector, rusted fuel supply line...? Link to comment Share on other sites More sharing options...
naru Posted March 15, 2009 Share Posted March 15, 2009 Save yourself some time by checking fuel pressure. Link to comment Share on other sites More sharing options...
derburger Posted March 16, 2009 Author Share Posted March 16, 2009 Low fuel pressure would tell me...? High fuel pressure would tell me...? My XT is either of those two problems. And connect the gauge where? It'll be another week before I can work on the car again. I replaced the fuel filter with a new one. Connected another fuel pump, that one makes noise too. There's a vibration from the high pressure line coming from the pump, no vibration from the low pressure. Then, I blew out the supply and return lines, after the gas was out, I blew out rusty powder . That's a problem... I replaced a few more hoses by the driver's rear tire that looked suspect, and noticed that the (fuel pump to fuel filter) line wasn't secured well and could be pushed and pulled around. If the fuel pump is cavitating, then it's not getting enough flow from the fuel tank. I think there's a pickup filter in the tank. I put in a new gas tank a few weeks ago, I don't even know if it has a filter in it or not. I guess I could disconnect the large supply hose at the fuel filter, and blow compressed air through to clear the filter? Bad return fuel pressure regulator so the fuel pressure is too high at the pump? I'll pickup a pressure gauge next week when I can get to working on this car again. This car is kicking my butt Link to comment Share on other sites More sharing options...
naru Posted March 16, 2009 Share Posted March 16, 2009 High pressure= bad reg or reg vacuum line,restricted return line or way wrong pump Low pressure= restricted filters,restricted or porous suction line,bad pump,bad pump voltage,restricted supply line,bad reg Tee the gauge in on the engine side of all filters.Make sure connections are VERY SECURE. Don`t want no flamethrower! Unless you have an electric one,tape the gauge OUTSIDE the windshield and try a heavy throttle run up a long hill. I wouldn`t blow back thru the tank filter. Link to comment Share on other sites More sharing options...
derburger Posted March 16, 2009 Author Share Posted March 16, 2009 My bet is on the pressure regulator being bad, causing high pressure in the pump lines. Nothing happened when I took the regulator's vacuum hose off. I removed the fuel filter and got a tremendous gas spray, even after I disconnected the fuel pump and ran the engine, and very little gas came from the return hose when I disconnected it and blew it out. Of course this doesn't mean much until I get a pressure gauge. I was just at Harbor freight this weekend . I might just order the pressure regulator along with a new radiator from Rockauto and replace those next weekend. Link to comment Share on other sites More sharing options...
derburger Posted March 22, 2009 Author Share Posted March 22, 2009 An update, fuel problem solved for now... I installed a new fuel pressure regulator, and I think that was my problem. It must have been stuck closed and causing high pressure in the fuel system. Now the car runs great without hesitation, no noise from the fuel pump (and now when the green plugs are connected in the trunk, the pump cycles normally and doesn't sound like it's sucking sand after a few seconds) I'll pick up a fuel pressure gauge next time I'm at harbor freight to check the pressure for reference. The fuel before the fuel pressure regulator was very rusty, it must have clogged the regulator somehow. I have a set of 4 injectors that I'll swap in later, running on junk fuel must have been bad for the ones in the car. The idle is a little funky still. When the car is started after running it idles at 800-900 RPM, cold starting about 1200, but during driving of the car, it idles at 1400 at a stoplight, for example. When I unplug the idle air control valve, nothing happens, I've looked everywhere for vacuum leaks, cleaned the coolant temp sensor and grounds. However, I've gone through the fuel and cooling system, and the XT should be a "somewhat reliable" daily driver for now. Link to comment Share on other sites More sharing options...
88glonthadl Posted March 8 Share Posted March 8 did it work indefinitely? Link to comment Share on other sites More sharing options...
Steptoe's photos Posted March 23 Share Posted March 23 wow ! try dredging up a 14 year old post on Facebook ! Link to comment Share on other sites More sharing options...
el_freddo Posted March 24 Share Posted March 24 7 hours ago, Steptoe's photos said: wow ! try dredging up a 14 year old post on Facebook ! I’m hoping there’s a reply answer! I’m enjoying some of the thread digging going on - it’s good to see ppl doing searches on the forum, via google or otherwise. Cheers Bennie 1 Link to comment Share on other sites More sharing options...
Porygon Posted June 7 Share Posted June 7 On 3/7/2024 at 7:24 PM, 88glonthadl said: did it work indefinitely? Yes, no more fuel problems for the 10yrs or so I owned that car. (lost the email address to OP's account) 1 Link to comment Share on other sites More sharing options...
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