Wont stay running

[4inlift94ranger]

So I got a little issue. Every now and then when i start my truck it does this thing where it does actually kick over, but the rpm's will come up but will not stay up high enough to keep it running before it goes down to almost nothing and dies. ive tried stepping on the gas to see if that will help and it doesn't. I put in a new fuel filter so that isn't the problem. Note: it only does this every so often. when it does, all i end up having to do is wait a while and then it does what it is supposed to do. im thinking maybe a sensor but im unsure which one. mass air flow maybe? also when i am at an idle maybe at a stop light the rpms come way down to the point i worry about it dying out but usually doesn't. any thoughts are helpful.

 

[black_demon69]

So I got a little issue. Every now and then when i start my truck it does this thing where it does actually kick over, but the rpm's will come up but will not stay up high enough to keep it running before it goes down to almost nothing and dies. ive tried stepping on the gas to see if that will help and it doesn't. I put in a new fuel filter so that isn't the problem. Note: it only does this every so often. when it does, all i end up having to do is wait a while and then it does what it is supposed to do. im thinking maybe a sensor but im unsure which one. mass air flow maybe? also when i am at an idle maybe at a stop light the rpms come way down to the point i worry about it dying out but usually doesn't. any thoughts are helpful.

sounds like fuel pump

had the same problem awhile back

 

[black_demon69]

before you go just replacing pump check and repair or replace as necessary fuel pump relay, inertia switch (just above carpet on passenger foot well), wiring and connectors, and fuel Pressure. not necessarily in that order.

 

[Big Jim M]

What we don't know is if the engine does run all day after finally starting. If YES then do this. First thing in the morning turn the key to the run position and allow the fuel pump to pump up the fuel system. Then after 10 secs or so try to start it. If it doesn't start do the key on thing again. If this helps then your problem is fuel leaking back into the fuel tank. This is a common problem and can be repaired easily. Or it can be ignored and started in the same manner.
As for depressing the gas peddle, all this does is add AIR and will only help in flooded situations. For cold starts doing that only worsens the mixture needed to make the engine run.
Big Jim

 

[enjr44]

Do what Jim said; but, do it three times. Turn key on, wait a few seconds, turn off. Repeat three times. On the last cycle go from off to start without stopping at run. The computer turns the pump on for 2-3 seconds when key goes to run. It does not restart pump again until engine rpm is above 500 rpm.

If it starts normally, then the fuel pump check valve could be leaking, causing no/low pressure to the injectors at start up and the engine dies before the pump can recover. The check valve is in the fuel pump and you can't just replace it. There is a fuel pressure regulator in there someplace; but, I don't think it does anything at start up, since there isn't any vacuum, at start to operate it.

You really need to check the fuel pressure at the rail. Rent, borrow, etc. a fuel pressure tester. Fuel pressure on say a 2.3, should be above 30 lbs and hold with key on engine off and something above that with engine running.