1991 Isuzu Amigo Fuel Pump Problem

Most fuel injection vehicles today have enough intelligence that the fuel pump will only run a few seconds while cranking and then turn off if the engine won't start. (No need to flood piston with more fuel.) So the only thing your test tells you is that the fuel line is not completely blocked and the fuel pump is not dead. If you intend to do your own repair work, find out how to get information from the "brain" that controls all of the systems. You maybe able to read the error codes from the flash cycle of the check engine light with the correct pins connected. This method does work (in those that have it) but is a real pain and prone to code translation error. Buy the computer reading box and see what it says.

You might also try swapping the fuel relay if it is the same as another one in the car. If this fixes the problem than the relay is bad.

Similar problem here with a Briggs & Stratton 50cc lawnmower engine. _{<Subscribes to discussion>}

From here, I would think the on board computer is not interfacing correctly with the drive-line computer.

Or, there may just be a restriction in the fuel delivery system. Common places are the fine screen in bottom of the fuel pick up in the tank, or inside the end plate of the carb.

On the odd chance that you do not have the scan tool used by Briggs, try choking the salesman carburetor after it starts.

Many of the GM vehicles of this era used the oil pressure switch to supply power to the electric fuel pump after starting. Find the oil pressure switch, and check for the number of wires on it. If it only has one, that is not the switch for the fuel pump. It will need at least 2 wires, and could have three. The two wires that are heavier will be the supply and delivery of power to the pump. The pink, or red one for power with the key on, engine not running. If power is not there, check for blown fuses. If there is power there, jump across to the other heavy wire. That should cause the in tank pump to run. This should allow the truck to run now. If so test continuity through the switch with the engine running. You do have oil in it don't you? Good luck.

I do not know much about cars, but the only possible cause of your problem might be on the idling injector, the relay on your idling injector might be faulty thus failing to supply fuel on your carburator to maintain idling.

I have a '98 Isuzu Rodeo and have had this issue before. The first couple of times it happened it was actually the MAF (mass air flow sensor). To fix it I bought a can of electrical contact cleaner and cleaned the sensor with it. Maybe a half hour job to remove the sensor, clean it, let it dry and put it back in. All I needed was a screw driver. This lasted about 6mos and then the whole unit had to be replaced, that cost me around $100 and has been working fine for two years now.

I have had other problems over the last year that are similar. A diagnostic has shown that for some reason the vehicle thinks it is running too rich and pulls the air-fuel ratio back until the engine cuts out. I have errors that read out a problem with the 02 sensor but that isn't it. All I know is that it corrects itself after I get in there and poke around a bit. I know this paragraph isn't much help to you, but maybe someone else will be able to build off of it.

Good luck!

K

yeah same thing happened to me, never would have guessed it though

A test light tapped into the wire for the fuel pump will identify if there is power to the pump in the run position.

I have a friend that had one. It wouldn't start at all. He would shoot either into the intake to get it to run when it was cold. I helped him lookup the troubleshooting procedures and they were very involved. I doubt you'll find an easy repair. I'd look for a shop that has a track record on Isuzu's or it will probably cost you a bundle to get it fixed. Good luck.

If you are willing to test in a logical order, with simple hand tools, we will be able to resolve your problem right here. Your vehicle has it's own problem. It may be the same as some one else's problem. But it will not be the same as every one's problem. Don't guess, test. Look at some of the other automotive threads here. We have found some strange ones. Just work your way through the tests one at a time. Good luck.

Relay($13 at rockauto), is priming but not suppllying. Thats why it starts right up(priming) then dies (lack of supply.)

Relay=

Stage 1: the Prime, then the truck starts.

Stage 2: fuel supply is kicked on(if not the truck dies.)

The fuel system is turned on by the ECM for about 1 second when the engine is first turned to the run position. When the key is moved to the start position, again the fuel pump is energized. When the switch is allowed to return to the run position, the oil pressure switch now supplies power to the fuel pump.

If I were looking for the cure, I would test the wires on the oil pressure sending unit.