On my 1999 F350 SD Crew Cab, 6.8l V10, it will crank, but won't start. I have checked fuel pump fuses and relays, and all are good. I checked the "collision switch" and it is good. I pulled the fuel pump and connected it to the battery and it works, but there is no voltage at the fuel pump connector nearest the fuel pump. I have spoken to a Ford mechanic and he said that if their is voltage from the output of the collision switch, that it must be a wiring problem between the switch and the fuel pump connector, but I have but I have been unable to find a problem. Can anyone suggest anything else to try? Thank you.

 

So when you turn the key on you are not hearing the fuel pump com on and prime the engine for 3 seconds .
I would get under the truck, with safety glasses on, because what you are about to do , is going to knock dirt and crap into your face and eyes.

That said, start at the fuel tank, and the harness runs along the driver side of the frame rail.
Check the entire length of that wiring , for visual damage .
Hopefully you have some sort of a repair manual, like a Chiltons , that has a wiring diagram in it .

Most of the connections are close to the back of the fender cab area, check for loose or damaged connectors.

 

my money is on the fuel pump ground.

 

My money is on a mis-diagnosis due to not fully understanding how the circuit works.

You have a grand total of TWO SECONDS from the time the ignition switch is turned from OFF to RUN (not START) to make your fuel pump power measurement, after that, the PCM turns the fuel pump relay back off and any measurement made thereafter is invalid until the PCM starts a new priming cycle or the engine fires.

TWO SECONDS! Memorize that!

Now, go back and redo your measurements keeping that timing window in mind and report the correct observations.

 

100 percent correct..


also you removed the pump..... by doing so.. you may have disloged crud .. so it worked on the bench.. putting it back in.. could have made it stop working again...


seen people do this several times.


but.. Voltage must be checked FIRST.. a MUST. and 2 seconds..
better to have a second person.. one for the KEY.. other one to view meter.

 

Just listen to the pump to run for those 2 seconds. or measure..

 

First of all, it is 3 seconds (not 2) and I have my multi-meter connected and positioned to where I can see it easily from where I am when I am turning the key. Second, I decided since I was at 150,000 miles to replace the pump (since I already had it out) and it tested fine before I installed it. I rechecked the output voltage after the inertia switch and it is 12vdc for 3 seconds. I did notice that the fuel pump relay doesn't engage...something I wasn't able to check before and now have. I have also learned that the oil sending unit can kill the fuel pump power, so I will have to look at that as well. With the fuel pump relay not energizing, I will also look at the PCM, since that controls that relay''s coil.

It makes me truly appreciate my '64 p/u where I could get into the engine compartment with the engine to work on it and there was none of this computer crap to deal with. Depending on what I find out in my further testing, I might just run new wires to the pump and see if the truck starts. That will eliminate numerous possibilities.

 

See now.. if you had offered this information before...


and What does it matter if 2 or 3 seconds... its STILL a very short time..


and not a thing was said about installing a new pump..


Best of luck with your no start issue...


and I worked on 1964 trucks when they were 4 years old. I started at the dealership in 1968 as a mechanic.


almost every external part needed to be replaced every 3 to 4 years..
my last car went 19 years before needing ball joints/tie rods.. or hoses..

 

That's totally cool. My dad bought his 1964 from his boss in 1965. Growing up, I learned how to repair vehicles on cars and trucks from the late '50s and early '60s. My first car was a red with a white top, 1959 Rambler American Station Wagon that my granddad had promised to give me ever since I was a very small child...I loved that car.

When I moved to Baltimore, my dad gave me his 1964 Chevy C20 so I could pull a trailer. Neat truck. When I sold it in 2001, the original wood bed was in perfect condition. I am a real fan of vehicles from the teens to the 'early '60s (especially trucks).

Every vehicle I have owned from that time period lasted with little maintenance (besides normal maintenance) for nearly 300,000 miles ( over 300,000 miles) and 30 - 40 years before I eventually sold them and they were still going strong even then.

I do have to admit that this truck is the nicest truck I have owned. It is like a car inside and having a Crew Cab, it is perfect for my 4 dogs (or multiple passengers) to be completely comfortable.

I decided to replace the fuel pump after talking to a Ford tech and a couple of people I spoke to had also been told by Ford techs, "they (fuel pumps) last about 100K miles", so I took advantage of the fact that I had removed the bed to get to it, so it would be a very easy access.

Take care.

 

Then you should have stated that you made that specific observation. 99% of posters who state they have no power to the fuel pump do the test wrong and end up out in the weeds beyond left field which is where it sounded like you were.

Those are contradictory conditions, you cannot have power at the inertia switch without the fuel pump relay supplying it, it is the ONLY thing (other than a wiring fault) that can supply pump power.

No, it doesn't. The oil pressure sending switch only goes to the cluster for the idiot light functions. The circuit has no effect on the engine's operation in this era of vehicles.

Moving forward:

Verify switched power at the output of the IFS for the priming cycle. If you have power there but the pump motor does not operate, you have an electrical circuit fault (open circuit).

Disconnect the IFS connector and measure resistance between the pin that goes to the fuel pump and chassis ground, should measure about 10 ohms or less. Yo're measuring the complete wiring circuit plus the fuel pump.

If it measures open, you need to find the open circuit. Break the circuit down. Check the wire from the IFS switch to the fuel pump. Check the wired from ground to the fuel pump. Both should measure near zero ohms. (Shortcut: Disconnect pump, install a jumper in the harness side of the connector. Checks two wires at once.) If both are good, then the problem is in the fuel pump module assembly or its wiring, you'll have to check each wire and connection individually. If you get down to the fuel pump motor itself showing the open circuit, tap it a few times and recheck, might be intermittent brush contacts. Just because it's new does not guarantee that it is good.

 

I am not sure what else to check as it is not showing an open condition. Since I don't know if the fuel pump relay is supposed to be in the un-energized position or not and then having it not move and switching other relays to rule out a bad relay, I'm not sure what to think. The tech at Ford said that the power goes directly from the IFS to the fuel pump, but when I tried tracing the wire from the fuel pump forward, it lead me to the fuse/relay box under the hood.

I hope this gives you something to go on, because there is something wrong...and I believe it is electrical, but everything I check (so far) checks out good.

PS: I don't know how to quote individual lines like you did. That is why I put my responses in blue italics.

 

I think you ought to get a wiring diagram. However, if you want to go without it, I would be tempted to run a jumper wire. That is just the way I am. If it starts under those conditions, you can keep working on finding a wiring problem.

This should be obvious, but all these components could be easily bypassed if you are confused about their intended states. You should not have to go through life confused about whether or not you have fuel pressure. That's no way to live.

I like to know I am on the right track.

 

Right on needing the wiring diagram. There are a few relays for the fuel system on the V10 truck. There is the fuel pump relay, the speed relay, and also the resistor.

I can get you diagrams if you want them. let me know your email and I'll send them.

 

That would indicate you maybe traced the wrong wire. You should be tracing the pink/black wire. See below.

The 99 V10 had only one fuel pump relay, no dropping resistors unless it was "California" specification truck. If so, then it (the pink/black wire) does go back to the power distribution box for the extra circuitry.

Look at the underside of the hood and see if the emissions compliance label is still there and legible.

 

Got one in the garage, federal. Two relays and a resistor.