packfancjh

Hey guys I have a problem going on right now. I have a 97 F150 with a 4.6L motor. I drove it Sat morning got home and parked it. Went out a few hours later and tried to start it but wouldn't, kept turning over but wouldn't start. I pulled the fuel line off the fuel filter to see if it was pumping gas but nothing. I checked the fuse and relay and both looked good and there was 12 volts on the relay. There was 12 volts at the inertia switch and the plug for the fuel pump so I figured it was a bad pump. Went and got a new one and put it in but no change. Where can I look next. Out of curiosity I bench tested the original pump and it worked just fine so I know the problem wasn't the pump. Thanks in advance for any help.

JRV

Always check a no start situation with 3 things: Fuel/Spark/Compression.

That was not a bad idea to replace the pump, but what you needed to do and still DO need to do is get a fuel pressure gauge on the truck and see where you are at there. If the pump is good, you probably have good pressure, but you still need to check it as part of diagnosing the problem.

Next place to start looking is for spark to see if the problem is ignition related. More than likely, its going to be something simple. Don't get worried just yet - check for compression last, because most likely it is a fuel/spark problem. Pull a plug and check for spark - if you aren't getting any, then you have the problem found, you just need to find what part is causing the problem then. Coil packs...injectors...ignition module...we'll be able to help you out better once you narrow it down for us just a bit.

packfancjh

I took the fuel line off in front of the fuel filter and tried turning it over but no fuel came out. That would tell me that I have no fuel pressure right?

Good old Bill

Doesn't this vintage truck have a pump on the frame also? JRV, this ones for you,"Always check a no start situation with 3 things: Fuel/Spark/Compression", we need to add one more item to your 3 things. A true story, get a call on the radio, Bill, workman no start. Go out to the 16 fairway where Jose was working, found he parked the workman over an irrigation head so he wouldn't get wet when it turned on. It worked, he didn't get wet but the frame mounted air filter was full of water and hence no air to the engine.

packfancjh

The filter is on the frame but the pump is mounted in the gas tank.

JRV

Bill does bring up a good point - these trucks do hate water anywhere and around the engine bay. Did you wash the engine? Normally they'll still start, but just run bad.

Your best bet is going to be to hook up a fuel pressure gauge. Autozone probably has one you can rent for a little of nothing. Just hook that gauge up and turn the truck over, and see what she reads. I don't know what our trucks are supposed to be at for pressure though. Have you changed your fuel filter? Also, how long were you cranking the truck? Maybe you've basically flooded it from cranking so long. Hold the gas to the floor so that it will stop sending fuel and see if she fires.

I'm not sure what fuel line you have pulled off, but that doesn't necessarily mean you aren't getting pressure to me. The gauge won't lie to you...just hook onto the schrader valve (which should be located on the passenger side fuel rail - looks like a valve stem on a tire), crank your truck and see where you're at. That is most definitely what I would do after replacing the fuel filter, hopefully somebody else will agree.

If you have pressure, move on to spark. When you pull a plug, see if it is soaking wet or not, which is another tell that you are at least getting SOME fuel, but no spark.

Good old Bill

"There was 12 volts at the inertia switch and the plug for the fuel pump so I figured it was a bad pump." With 12 volts at the pump and no fuel at or from the filter, is the ground good? Can you hear the pump run for 1-2 seconds when switch is turned on? Is the filter plugged? Sorry about the frame mounted pump error, brain remember 87, not 97 vintage.

packfancjh

I pulled the fuel line off of the inlet end of the fuel filter which is the first connection in line from the gas tank. As I crank it over no gas comes out of that line. I usually crank it for 10 to 20 seconds. I did replace the filter at the same time I replaced the pump. If there is no gas coming out of the line 4 feet from the tank I would think there would be no pressure all the way at the engine at the von shrader valve.

packfancjh

I cannot hear the pump kick on at all. Where would the ground for the fuel pump be?

Good old Bill

OK, the pump is not running at all. Just a reminder as to pump operation. Turn key to on, pump runs 1-2-3 seconds. It will not run again untill engine starts. Go back to the connector at the pump, the black wire is ground, should be G104, if someone has the EVTM manual showing locations of the ground terminals. Anyway, find the black wire in the loom going to the pump, with an ohm meter probe it and test for continuity. Lower the tank again and retest new pump, perhaps its bad or connection is faulty. Your troubleshooting technique is right on, go with your gutt, you have to get gas to the filter to make this thing run.