Truck died on the road. Power going to distributor but not coming out. Also, fuel pump not pressurizing when key is in run position. Replaced the distributor completely, fuel pump relay and the ecm. Still has the same problem. Could it be the camshaft sensor?
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The fuel pump is suspect but I believe there's also a fuel filter inline on the underside of the drivers side chassis. Fuel works off pressure so if the filter is clogged, the pressure remains between the fuel tank and the filter. Once the fuel has siphoned off between the filter and injectors, it dies but because there's positive pressure at the fuel pump, it won't come on until the pressure slowly seeps past the clog after hours. It's worth a look!
Low pressure from fuel pump, when the pump is cold the pressure increases, as it warms up the pressure drops (this happens in a pump that is going out) the normal pressure should be at 40 with the key on and engine not running, when started the pressure should stay around 36, any less it won't idle and may run as long as you hold the pedal down. The injectors are opened electronicaly, so as long as there is fuel flow the engine gets fuel to run.So check the fuel pump, soundslike you need a new one
Yes, it should. If it is conventional (like other GM cars), the pump will turn on for a couple of seconds when key is turned to on. This will prime the system for starting. When key is turned to start (cranking), the pump is turned on again at the relay, and pump stays on as long as cranking the engine happens. Once engine is started, the oil pressure switch keeps the pump running.
The best way to check if pump is good is to use a fuel pressure gauge. If it does not have a test port called a Schrader valve on the fuel rail, the pressure gauge must be teed in somewhere convenient. But if you take off the line at the filter, some gas should come out with key on, and when cranking the engine gas should come out in a steady stream.
Modern fuel injected vehicles will only run the pump for a couple of seconds to pressurize the fuel system at stat-up. The pump won't run after that until the engine is running or you are actively engaging the starter. The fuel pump and relay are doing exactly what they are supposed to do. Now, that doesn't mean the pump is building pressure like it should but the pump running for a second then shutting off after you first turn on the key is normal operation. You may have entered it, but I can see no information about what vehicle you are working on other than it is a truck. More information about the vehicle would help. In the mean time, I feel a compression check is an order and you should take a look at the oil to make sure there isn't any water mixed in. Some history would help as well, like if you have done any type of service in the last month, when the basic maintainence was done, how many miles are on it, etc.
It is normal for the pump to run for two seconds when first switched on to pressurize the fuel system. It will turn on again when cranking and while running. I would still suspect the pump given your symptoms, however other problems could also give you the same symptoms. If it is the original pump from 2002, or more than about 7 or 8 years old, I would definitely replace it, and the fuel filter. Often the pump will go intermittent. I had one that I could restart and get down the road by hitting the bottom of the gas tank a few times!
Turn on the key and listen by the fuel tank for the fuel pump to hum. A common problem is low fuel pressure. It will build pressure when the key is turned, use that fuel, and then the pressure drops. Kind of like when you're using a squirt gun that's getting empty.
try bypassing the oil pressure switch on the back of the block behind the distributor, if there oil pressure switch goes bad it will do this. had one that drove me nuts trying to fix it then figured out I had to buy a book and low and behold thee it was 3 wire oil pressure switch you can't see between the engine and fire wall just behind the distributor and costs 8 bucks to buy new.
85 with TBI only needs 13lbs of fuel pressure. verify that the fuel filter is clean. there is no easy way to ck fuel pressure, special adapters are needed, I dont have info here at home but there should be a relay for the pump, on the firewall and the oil pressure switch also powers the pump. did you replace the pump trying to fix this problem or did you just mention it to help troubleshoot the problem? verify that the fuel pump wiring has a good ground, should have been a eyelet that bolted to the frame..when you initially turn the key on, you should hera the fuel pump power up for 2 seconds, then go off, after the engine starts, the power for the pump goes through the oil pressure switch.