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GMC Jimmy Fuel System

gator14gator14 Posts: 5
My jimmy would run for awhile then stop. Let it sit for awhile then it would start. Changed the fuel pump same thing, changed the relay same thing, changed the ecm same thing. was told to check the oil presure swith but don't know where it is. Dose anyone know (help)



  • 4.3 is back by the distributor on a small pipe so look for the electrical connector. Look at the part online or at a store and see what it looks like then you will spot it. You sure its fuel related and not spark (coil, ign module, etc) as it heats up?
  • yep cause if you hot wire the fuel pump and some one pours gas into the TBI it runs great. i figure this is the only thing left to change ( i hope).

    gator 14
  • Not sure which motor 4.3 or 2.8 you have or if CPI or the older TBI with the fuel metered into the top of the "carb".
    Did you check the ECM (may be 2) and ENG fuses also? CPI needs higher pressure like 60psi to start while TBI is like 12psi.
  • Well we got it going. Turned out to be broaken wire from the key to the relay. We just jumped the relay and it works. Thank you all for the help..

    Gator 14
  • I have a 97 Jimmy that will not build fuel pressure. If you give it starting fluid it will start and run on the starting fluid but then die when you stop feeding it. No pressure at the rail. Other symptoms I have found are that the oil pressure gauge stopped working (Stuck on 20 PSI). The fuel gauge shows just under full and it only has about 1/4 tank. It will not come out of park. All these things worked fine until the fuel issue. I have changed the fuel filter and found that it was pretty well blocked off. I have read that there is a fuel pump run wire under the hood. Is this true? Where would I find it? Any other way to test the pump? I hate to drop the tank and change it out ($300.00) without knowing its bad. Especially since I have the other symptoms. What other types of fuel shutdown safety/security items are on this vehicle (IE. low oil pressure, inertia shutdown)?
  • repairdogrepairdog Posts: 948
    OK - checked Haynes again and the test wire is red and by the firewall and master cylinder. This bypasses the relay. Check the ECM Bat fuse that powers the relay and switch the fuel pump relay with another thats the same as a test. Also remember that the 97 only has a known ignition switch (actually a module with wiring in the column) failure and it effects most power on the vehicle as it runs thru there when the key is turned.
  • Powered the test wire and the pump works fine. Rotated the relays (the 3 in the glove box) and no change. Checked all of the standard fuses and they were fine. Is the ECM Bat fuse located in the regular fuse box by the drivers side door or some where else?
  • I have a 95 GMC Jimmy with 300000 kms on it, I have done the fuel pump, sending unit and have done repairs to the rotted out fuel lines. If it sits for more then 4 hours I have to use starter fluid to get it going. 2 hours it will start 4 hours is touch and go 6 hours forget it. I have been told the fuel lines need to be replaced because it is getting a air pocket in the lines. Any insight in to this situation would be appreciated.
  • replaced plugs wires cap rotor fuel pump, sending unit, and fuel pressure regulator it has 62 psi key on not running 55 psi when it starts but some times wont start unless you spray starting fluid in intake , gm dealer ran test on spider assembly and said al was good , what should i try next? can anybody help
  • repairdogrepairdog Posts: 948
    Could be sensor or electrical - any codes set the SES ever? I'd look at the electrical connectors, the crank sensor under the front of the engine by the bottom of the timing cover (tells ECM where timing is off the crank), all wiring/cables from the battery are clean and good (do not like low voltage), then other sensors (MAF, temp, O2 etc)but GM should have scanned the sensors and ECM, then a weak coil so plugs are firing but weak. Finally, when was the cap/rotor new and was it Delco and not a cheap aftermarket one - I fought one for several days that was under a year old and was arching in the plastic (can't see internal casting) so several plugs firing at once - changed and all well. Then also look at the vac lines for rot and replace 5/32 and 7/32" all that are bad. The cam sensor in the dist will not cause a no start only rough idle. Then the ign module in the dist fires the coil, but........Sorry, not a simple answer but again suprised GM didn't see anything. Haynes/Chiltons cover testing most of these with a simple multimeter.
  • replaced plugs, cap, rotor,good spark at coil and at plugs , no codes, starts up when you shoot it with starting fluid, and will stay running ,try to restart and also starts most of the time but when it dont have to reshoot with starting fluid maybee once a week
  • I have a 1994 Chevrolet S-10 Blazer with a 4.3L Vortec. Came home with no problems. Next morning it would not start. Mechanic cannot determine problem except fuel pump isn't getting power. I had the fuel pump replaced eight months ago. He said to take it to dealer for further diagnosing. Before I do, does anyone have any suggestions or opinions about what could cause the fuel pump not to be getting power? Please help!
  • The solution to my original post was the the starter switch (not the key but the switch attached to it). Apparently this is a common issue on the 97s
  • Fuel pump relay or fuses need to be checked and there is a red wire up by the brake booster that can power the pump bypassing all relays etc to test it - shop should know this or ....
  • Did you ever figure out why your 97 Jimmy will not build fuel pressure If not I can help. For starter's can you hear the fuel pump hmmm when you turn the key switch on and off? If so have you checked to see if fuel is flowing at all by depressing the shrader valve back by rear of engine and having someone crank engine. If fuel is flowing or squirts with key on engine off then you have pressure. You need 60 PSI to start the vehicle on a vortex setup. If all the above information is happening then you might want to check you Crank Position Sensor for resistance. If it does not have a signal, your MFI manifold will not fire the fuel injectors. If you Have no pressure at the shrader valve when depressed, with key on engine off then your fuel pressure regulator has gone bad. Hope this helps.
  • My 99 Jimmy was working fine in the morning when I came home, and when I went to restart it several hours later it would not start. Ignition turned over, and there definitely was gas in the tank, but I added some anyway, and it still would not start. I replaced the ECM fuse under the hood, and replaced several other fuses related to the fuel pump. No start. I then put gas directly into the carb, and the engine turned over but then died.

    From other discussions, I could not find this issue addressed for specifically the 99 Jimmy. It is a 4wd.

    Additional incidents that may be related:
    The service engine soon light was on for about a week, then was off for about two weeks. It came on again two days before this situation.

    The fuel gauge would read accurately until it got to about 1/4 tank, then it would jump to either full, or completely empty. I only ran out of gas one time due to this problem and that was about a year ago. Since that time, I have always kept fuel level high to avoid this and have used my trip odometer to keep me posted on fuel level.

    Otherwise, possibly unrelated, the dash lights for the radio and steering wheel are half lit, but recently the lights for the radio are completely dark. The heated seat for the driver's side stopped working during the last two weeks.
  • repairdogrepairdog Posts: 948
    Could be electrical and you need the code readout to see what tripped it (could be your answer -or not). To test fuel pressure need $35 fuel pressure tester and 60psi key on engine off and running 53psi min. Then could be simple cap/rotor problem so replace those. Next is test coil and ignition module mounted on it (stores test for free). Then crank sensor next. As to the lights could be just burned out and the seats check the fuse under hood for that baby - if the switch or wiring gets rubbed thru that can blow the fuse (your manual tells which is which and so does the inside of the cover). Let us know.
  • I replaced the ECM fuse and it didn't start, then I cleaned carefully the ports where you put the fuse into, thinking maybe dirt was in there, replaced the fuse, changed the oil, and then it did start. It worked for two days, and then after sitting overnight in the garage, it wouldn't start. I did put gas directly into carb, and it cranked. What about fuel filter?
  • repairdogrepairdog Posts: 948
    Yes, under the frame under the drivers side door area - a mess to do but not hard about $15 part. The only way to know about pump is to test the pressure. If pressure OK then its electrical/sensor and change the cap/rotor first, then check coil, and then crank sensor.
  • jlflemmonsjlflemmons Posts: 2,242
    I know this will sound crazy, but give the gas tank a swift kick. I learned this trick from a wrecker driver who said the common failure in the fuel pump was that it would stop at a "dead spot" in the windings. Gave the Yukon a kick in the tank when this same thing happened and bingo, fired right up. Took it to the dealer (warranty) and one of the mechanics admitted that they did the same thing when one came in on the hook and they didn't want to physically push it into the shop for the pump replacement.
  • Hello,
    I am having similar problem with my 98 4x4 Jimmy did you figure out what the problem was?

  • It actually worked for about two weeks, and then shut down again. We've been in snow for that time, so I didn't get to take the advice of repairdog and change the fuel filter. It's sitting in a parking lot, and as soon as I can tow it home (snow is everywhere making it difficult), I'll change the filter and let you know. Sorry can't be of more help right now. It cranks over, and when I put a shot of gas in the carb, it fires right up.
  • I am in a similar situation with the snow..At least my truck is the house. I changed my fuel filter too and my truck ran good for about a month, then started the same thing again. What diagnostic codes have you received? I get a PO147 which is HO2S Heather circuit bank1, sensor 3. HO2S is Heated Oxygen Sensor. According to some info I found..When the ignition is turned on, battery voltage is supplied to the HO2S heater to provide for faster sensor warm-up,thus allowing sensor to become active in a shorter period of time. When the temperature warms up more I am going to trouble shoot HO2S heater sensor and probably install new O2 sensors since my truck has 160,000 miles on it and they haven't never been changed. Keep in touch since it seems we have about the same problem. We might be able to help each other out by sharing info.

    [email protected]
  • I currently own a 1991 Jimmy, but it has many problems. The jimmy i have now is 2 door, dont know if that matters, I just bought a 1993 4 door Jimmy and the only thing wrong with it is the fuel pump regulator. I was wondering if I could take the fuel pump regulator off of my 91 jimmy and put it on the 1993 jimmy I just bought. If you know the answer please email me at [email protected]
  • repairdogrepairdog Posts: 948
    Look both years up on the online auto sites and see if the same. I would go new as its the labor thats the pain.
  • aaron13aaron13 Posts: 1
    Can someone give me some advise on my v6 4.3 Jimmy? my truck will run for a while about 10 or 12 miles I will stop the engine for a few minutes and try to start it again and will not start. Pump will not have electrical power (no noise on the pump). after a few minutes the truck will start again and can hear the pump running again. I have put a new gasoline pump, a new gas filter, a new fuel pump Relay. What else can I try? any sensors any where?
  • jim102jim102 Posts: 5
    Hi, Just wondering if you have figured out what the problem is with your Jimmy. I have been having similar problems with mine for the past year and a half. Replaced the fuel pump, and wires. It will sometimes start, sometimes not. There has already been a hole cut in the back of truck so top of pump is exposed where previous owner obviously had problems. I can open the back tap on pump a few times and usually it will start. Sometimes the pump will shut off when I am just driving down the road. I can't seem to find any explanation for why it is just shutting off. Any advice?
  • repairdogrepairdog Posts: 948
    Airtex makes a replacement connector for the top of the pump that may solve that. Must also have a good ground. Hope the pump put in was a Delco cause many others fail in a year so do a pressure test key on engine off and then running. Min of 60 psi KOEO and then 54 or so running.
  • slim10slim10 Posts: 1
    I have 97 s-10 blzr with fuel pump issues. The red test wire mentioned to bypass the relay, is it an open wire with a female spade connector on the end or is it attached to a junction or terminal? Thanks
  • 97jimmy197jimmy1 Posts: 4
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