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2002 Fuel Pump Troubleshooting (intermittantly dies)

 
  #1  
Old 08-23-2015, 11:32 PM
cokeman
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2002 Fuel Pump Troubleshooting (intermittantly dies)

I kind of hijacked a thread on a 99 with similar issues here:
99 F250 Cranks but won't start. only happens intermittently

The 99 has a separate relay while the 2002 in integrated in the junction box (fuse panel) so I thought starting a new thread would be better.

Basic symptoms. Truck will randomly die while driving. Once dead, turning the key on does not power up the fuel pump. Everything else electrical works fine. After a few minutes of sitting, turning the key gets power to the pump and the truck starts. Might run the rest of the day, might die again in a few miles.

Symptoms are totally random. Problem was that I could never get it to die in my driveway so I could test. The only pattern I thought I had was that when it died, it was almost exactly 3 minutes to wait before starting again. So that seemed like something getting hot then cooling down and making the connection again. I think that is wrong now.

I finally was able to get the truck to die in my driveway and did some testing. I think the fuel pump is good and the relay in the junction box is bad. When the truck dies, there is no power on the green/yellow wire that comes out of the fuse box and goes to the inertia switch. I do have power to the fuel pump fuse and the fuse is good. Inertia switch is good as well. Once power comes back to that G/Y wire, truck starts. I can put power on that wire and hear the pump run. So it has to be the integrated pump relay, right?

A couple of observations. It died last weekend when I got caught in a downpour and wouldn't start for several hours. Yesterday, I ran a hose all over the truck thinking maybe something getting wet was the cause. And I did get the truck to die, but I can't see where that could be the case and it must be coincidence. Only a little water gets under the hood and none in the cab. So if this was from something under the hood or in the cab getting wet, then other systems besides the fuel pump would die too.

If you made it through that wall of text, thanks. I just need another set of eyes on my findings to verify that I need to buy a new junction box and not a fuel pump. So I would appreciate any input. The other thing is timing. I am going to have to drive this truck the next few days. No way around it. So to keep myself from getting stranded, I think I can bypass the relay and send power to the pump. Nothing permanent just power when the relay dies. As long as I go through a fused circuit and inject power before the inertia switch, I think this should be fine. Right? It is still fused 12 volts, I can still have the safety shut off in case I am in a wreck, and I will only hook it up if the relay dies. Of course it may never die again until the new part arrives, but I need the option.
 
  #2  
Old 08-25-2015, 01:28 AM
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Your temporary bypass should work just fine.
I'm planning on adding that for test purposes when I find the time.
If indeed the relay is bad why buy another fuse panel with the same built in relay?
Wire in a standard relay available at many parts houses and bypass the one in the panel. Then carry a spare.
I think I saw another thread where that was done.
I have a 2002 Ex and plan on doing that when mine goes bad.
 
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Old 08-25-2015, 02:17 AM
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I may just wire in a relay, but I'll have to do some more testing first if I want it to act like the built-in relay. Normally, when you turn on the key, the pump gets power for a second or three to prime the pump then shuts off until you turn the key to start. Then the pump gets constant power after the truck is running. Looking at the wiring diagrams it seems what triggers the fuel pump relay is PCM power relay on the hot side and the diagram shows the PCM itself toggling the ground on the ground side. There are other components on that same hot side feed that always have power in start or run. So that tells me that the ground toggle in the PCM is what controls the prime and run timing. I could possibly utilize that and get stock behavior, but I don't know that for sure yet. Otherwise, I would have to just always have power to the pump anytime the key is on. Not sure that is a great idea.
 
  #4  
Old 08-25-2015, 10:27 AM
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I'm not sure whether this safety feature was included in your 2002 truck, but most FI vehicles include a shock switch that shuts down the fuel pump in the event of an accident. The last thing you want is a fuel pump that continues to spray fuel through a ruptured fuel line onto hot engine parts or onto the vehicle after an accident.
 
  #5  
Old 08-25-2015, 10:34 AM
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Originally Posted by KellyfromVA View Post
I'm not sure whether this safety feature was included in your 2002 truck, but most FI vehicles include a shock switch that shuts down the fuel pump in the event of an accident.....
The OP talks about the inertia switch in his first post.
 
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Old 08-25-2015, 10:50 AM
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Yes but if you bypass the switch by connecting a relay to the ignition on, an option that the OP suggested, that could present a serious safety hazard.
 
  #7  
Old 08-25-2015, 11:30 AM
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And in the last paragraph mentions "inject power before the inertia switch".
 
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Old 08-25-2015, 09:42 PM
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Yes, the inertia switch is still in the loop. So in the event of a rollover, the switch would (dis)engage and cut off the fuel. I think Kelly is concerned that if the circuit is always on with the ignition then there is a chance that a wreck that did not trip the inertia switch but busted a fuel line would let fuel spray everywhere. That is a valid concern, but I think anything that was hard enough to rupture a line would trip the inertia switch. Someone correct me if I am wrong, but that switch should trip on impact and not just on rollover. Hence the name "inertia" switch.

Thinking about this some more, I am going to check into a few more things before giving in an ordering an entire junction box. I have never been the type to just give in and order a new part if I can fix it. I have salvaged many an electronic device by resoldering, repairing, or replacing components on circuit boards. This doesn't seem like it should be any different. I found a couple of resources showing the circuit board and the PCB relays there and I can get equivalent relays from Omron. I will take mine apart and verify that the fuel pump relay is in fact burnt up or the solder connection is bad. If so, and I'm sure it will be, then my decision will be: replace that onboard relay with another or just bypass that altogether and wire in a generic external relay that would be easier to get to and replace if it dies again. Both options have positives.

Either way, my intent would be to wire it in to maintain stock behavior. So the concerns in the first paragraph would be addressed.

One concern in all this though is: what made that relay go? Maybe the aren't using continuous duty relays so they just dies after this kind of continuous use. Or is the fuel pump really on it's way out and putting resistance in the circuit that causes the relay to overheat? Either way, the relay has to be addressed, but it will suck to handle this only to burn up another one because the pump is acting up.
 
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Old 09-06-2015, 01:12 PM
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I took the fuse panel/junction box apart last night to verify there is a burnt relay in there. Sure enough I found a relay with a burnt leg and that relay is attached to the fuel pump circuit. I am glad I took the fuse panel apart and did not just blindly order one of these relays though. The box is several layers of circuit boards sandwiched together and posts are connecting various circuits are soldered in and hold the entire thing together. T0 de-solder the relays, I would have to get to the underside of that board and that is not feasible with this design. Sorry, I didn't take any pics, but if you are taking yours apart to check this relay, there are 3 on one side and 2 on the other. Tee fuel pump relay is one of the 2. If you hold it panel with the fuses at the bottom, it is the top one. If that makes any sense.

So, I got out my wiring diagrams and wired in my own relay. No pics again, I suck, but I will give you the connector numbers and wires I used in case someone wants to tackle this on their truck.

I used a standard double-throw relay, but I do not need 87a, so I took that wire out of the relay harness. Now all I have is 30, 87, 85, 86, essentially turning it into a single throw.

Relay #30
I wanted to make this just like the existing fuel pump circuit, so I needed a fused always hot lead for relay-30. This truck only has the instrument panel power point and cigar lighter. However, the fuses and circuits are in place for other power points like in an Excursion or trucks with console power points, but the connector does not have wire for those. So instead of running a hot wire from the battery and putting a fuse in-line (which would have been fine), I modified that connector to give me a fused lead for relay-30. Connector number is c270d in the service manual. Pin #1 goes to fuse #2. There is no lead there on my truck so I just put my own in there and modified the connector to allow the wire to pass through.

Relay #87
This is the lead that goes to the inertia switch and eventually the pump. This is on connector c270a. That is the largest connector on the box and the only one with the slide locking mechanism. Pin 22 has a 16ga Dark Green/Yellow Stripe wire. That goes to the inertia switch. You can pull off your passenger kick panel and make sure you are getting the right wire. I cut this wire and connected the non-connector side to relay-87.

Relay #85
Power when in start and run. I just tapped into the feed from the ignition switch for this one. You can get this at connector c270c. It has 6 large wires on it. The one we need here is on pin 6 and is a 14g red with light green stripe wire. Don't cut it, just tap into it.

Relay #86.
To make this exactly like the existing fuel pump circuit, I used the lead to the pcm fuel pump control. This lead just connects a ground according to the programmed timing. Key on, pump primes for a few seconds, turn to start/run it is fully connected. This is on connector c270f. Pin 10 is a 18g light blue with orange stripe wire. Cut that and connected the non-connector side to relay-86

One concern is that the on-board relays had diodes wired in parallel to dissipate any spike from the coil deenergizing. I did not wire diodes into my circuit. But since I bypassed the circuit board, that may not be an issue.

Now I get to drive around and try to replicate a random failure that I may have fixed. If the truck still dies after this, I give up.
 
  #10  
Old 09-06-2015, 01:56 PM
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Originally Posted by cokeman View Post
...
Relay #30
I wanted to make this just like the existing fuel pump circuit, so I needed a fused always hot lead for relay-30. This truck only has the instrument panel power point and cigar lighter. However, the fuses and circuits are in place for other power points like in an Excursion or trucks with console power points, but the connector does not have wire for those. So instead of running a hot wire from the battery and putting a fuse in-line (which would have been fine), I modified that connector to give me a fused lead for relay-30. ...
Alternative: You would not need to go all the way back to the battery. When the fuse panel was moved to under the steering wheel in 2002 a junction block was used in the line. It is located on the fender liner just in front of the power brake booster. A large gauge unfused cable from the battery comes in one side of the block. The other side has 2 good size cables with fuse links in them going thru the firewall to the fuse panel. A cable could be added at the junction block post with an inline fuse and fed thru the firewall grommet to provide power for the new fuel pump relay.
 
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Old 09-08-2015, 11:17 AM
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Yeah, that's where I would go and not all the way back. I like using that unused circuit in the fusebox though. Looks cleaner.

On a funny side-note, I took the wife's Dodge Durango in for some recalls. On the list was a rewire and elimination of an integrated fuel pump relay. Tech says "this was a stupid design by Dodge where they put the fuel pump relay in the junction box...etc etc" I just grinned and told him I know exactly what he means.
 
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Old 10-11-2015, 07:24 PM
bigwillisF150
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Originally Posted by cokeman View Post
I kind of hijacked a thread on a 99 with similar issues here:
99 F250 Cranks but won't start. only happens intermittently

The 99 has a separate relay while the 2002 in integrated in the junction box (fuse panel) so I thought starting a new thread would be better.

Basic symptoms. Truck will randomly die while driving. Once dead, turning the key on does not power up the fuel pump. Everything else electrical works fine. After a few minutes of sitting, turning the key gets power to the pump and the truck starts. Might run the rest of the day, might die again in a few miles.

Symptoms are totally random. Problem was that I could never get it to die in my driveway so I could test. The only pattern I thought I had was that when it died, it was almost exactly 3 minutes to wait before starting again. So that seemed like something getting hot then cooling down and making the connection again. I think that is wrong now.

I finally was able to get the truck to die in my driveway and did some testing. I think the fuel pump is good and the relay in the junction box is bad. When the truck dies, there is no power on the green/yellow wire that comes out of the fuse box and goes to the inertia switch. I do have power to the fuel pump fuse and the fuse is good. Inertia switch is good as well. Once power comes back to that G/Y wire, truck starts. I can put power on that wire and hear the pump run. So it has to be the integrated pump relay, right?

A couple of observations. It died last weekend when I got caught in a downpour and wouldn't start for several hours. Yesterday, I ran a hose all over the truck thinking maybe something getting wet was the cause. And I did get the truck to die, but I can't see where that could be the case and it must be coincidence. Only a little water gets under the hood and none in the cab. So if this was from something under the hood or in the cab getting wet, then other systems besides the fuel pump would die too.

If you made it through that wall of text, thanks. I just need another set of eyes on my findings to verify that I need to buy a new junction box and not a fuel pump. So I would appreciate any input. The other thing is timing. I am going to have to drive this truck the next few days. No way around it. So to keep myself from getting stranded, I think I can bypass the relay and send power to the pump. Nothing permanent just power when the relay dies. As long as I go through a fused circuit and inject power before the inertia switch, I think this should be fine. Right? It is still fused 12 volts, I can still have the safety shut off in case I am in a wreck, and I will only hook it up if the relay dies. Of course it may never die again until the new part arrives, but I need the option.
I went through all of this including the bypass you speak of to get me by until I figured out I had to replace the fuse panel itself. $340 from China on ebay. Ive never had a shutoff since. Good luck. My truck is 2002 f250 5.4L btw.
 
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Old 10-12-2015, 10:22 AM
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Originally Posted by cokeman View Post
... One concern is that the on-board relays had diodes wired in parallel to dissipate any spike from the coil deenergizing. I did not wire diodes into my circuit. But since I bypassed the circuit board, that may not be an issue. ...
I was rereading this topic and I think there may be a concern with the diodes.
Do the diodes protect the circuit board, the ECU or the relay contacts?
For your rewire did you use a coil relay with built in diode protection?
I have used solid state relays (SSR) recently in our trailer and they work very well.
I think SSRs don't need spike suppression because there is no coil.
Have you had any more issues with the engine dying?
 
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Old 10-12-2015, 11:18 AM
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No more issues so far.

There are no diodes in the relay I used. I am still not sure what the diodes were protecting. My guess is the circuit board, but I know the ECM might need protection, so that would not surprise me. The way I rewired it though, the only lead connecting back to the ECM is the ground lead though so I don't think a spike will go down that leg
 
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Old 10-12-2015, 01:17 PM
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I used to think the only purpose of the diode was to stop arcing across the relay contacts.
Similar to the condenser (capacitor) in old distributors for the points (contacts).
This paper on Understanding Relays Autoshop101, particularly pages 11 & 12, was interesting - http://www.autoshop101.com/forms/hweb2.pdf
 

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