I have a fass 165 gph that I've had on my truck since 2014. Lately every other time I start my truck I have no fuel pressure and it stumbles.

I replace the relay in the wiring harness but it does it again. What's weird is that the fuse isn't blowing but the relay is.

Relays aren't cheap I need to figure this one out. Any ideas?

Loose connection will cook things up.

Ill double check where the fass harness plugs in to the stock lift pump connector, that's the only spot I haven't checked yet.

 

15 hours ago, Rotket said:

I have a fass 165 gph that I've had on my truck since 2014. Lately every other time I start my truck I have no fuel pressure and it stumbles.

I replace the relay in the wiring harness but it does it again. What's weird is that the fuse isn't blowing but the relay is.

Relays aren't cheap I need to figure this one out. Any ideas?

Did you make up the wire harness yourself or did it come from Fass with the lift pump? I suspect there is ground and positive wired wrong to the relay but don't quote me on that. The articles section on lift pumps has a diagram drawn by IBMobile that shows the relay numbers for each connection/ terminal and what they go to. I would start there.

8 hours ago, JAG1 said:

Did you make up the wire harness yourself or did it come from Fass with the lift pump? I suspect there is ground and positive wired wrong to the relay but don't quote me on that. The articles section on lift pumps has a diagram drawn by IBMobile that shows the relay numbers for each connection/ terminal and what they go to. I would start there.

The harness came with the fass system.

But if it was wired wrong it wouldn't have taken 6 years to show, right?

57 minutes ago, Rotket said:

The harness came with the fass system.

But if it was wired wrong it wouldn't have taken 6 years to show, right?

If it was wired wrong from FASS it would have shown the day you put in. I would open the wring and see if something is chafed or coming apart maybe. Maybe the socket is failing and arching causing the issue. I would think that would be visible when pull the relay. Just my best guess.

 

Edited February 13, 20205 yr by dripley

3 hours ago, Rotket said:

The harness came with the fass system.

But if it was wired wrong it wouldn't have taken 6 years to show, right?

Yes right! so sumpens crossed up somewhere.

23 hours ago, Rotket said:

Ill double check where the fass harness plugs in to the stock lift pump connector, that's the only spot I haven't checked yet.

 

That's only to trigger the relay coil, I suppose if it was intermittent it could cook the coil. Have you taken a bad really apart to see what's cooked? 

10 hours ago, Dieselfuture said:

That's only to trigger the relay coil, I suppose if it was intermittent it could cook the coil. Have you taken a bad really apart to see what's cook

No but i can do that. I just take them out and rattle them to confirm they're blown.

The first one blew a couple years ago when moisture got in the socket.

The pump doesn't sound abnormal or anything and the filters are new. I'm also not great with electronics so I might buy just buy a new harness for the fass.

Or I can splice in a new socket

Make sure you're buying a protective relay, with a resistor or a diode on coil side, it'll be in the diagram on top of relay. This way when it denergizes, current spike doesn't get backfead to ecm. 

You can slide pin connectors out of relay plug and see if they're corroded. I use dielectric grease on all connectors never had an issue in long run. 

On 2/14/2020 at 7:52 AM, Dieselfuture said:

Make sure you're buying a protective relay, with a resistor or a diode on coil side, it'll be in the diagram on top of relay. This way when it denergizes, current spike doesn't get backfead to ecm. 

You can slide pin connectors out of relay plug and see if they're corroded. I use dielectric grease on all connectors never had an issue in long run. 

Hmm could you give me a link to a protective relay?

On 2/16/2020 at 10:16 PM, Rotket said:

Hmm could you give me a link to a protective relay?

https://www.google.com/search?client=ms-android-verizon&ei=BWZLXrmFMMqxggekoq_IBw&q=car+relay+with+diode+or+resistor&oq=car+relay+with+diode+or+resi&gs_l=mobile-gws-wiz-serp.1.0.33i160i395l2j33i299i395l2.43795.47627..49195...0.1..0.135.936.0j8....3..0....1.........0i71j0i22i30j33i22i29i30i395.zvEb0JFZk_I

Update on this. I spliced in another relay socket because the other one was fairly corroded. Put in a new relay and it doesn't work the next morning.

I'm at a loss for what to do next. I can only assume that my pump is blowing these relays some how, but it doesn't sound unhealthy.

Might have to take it some where.

What size fuse are you using?  What part of the relay is going bad; the coil or the contacts?  Can you do an amp draw test to see how much the fuel pump is using?

On 2/23/2020 at 9:43 PM, IBMobile said:

What size fuse are you using?  What part of the relay is going bad; the coil or the contacts?  Can you do an amp draw test to see how much the fuel pump is using?

Sorry ive been dealing with my jeep too, so I'm just getting back to this. Chrysler products ya know?

I've used both 30 and 40 amp relays. They work on the first start but when I go to start it again, I get no fuel pressure and the pump stops working.

I'm not sure if the coil or contacts are bad. The first relays I could literally rattle, but the most recent relays weren't obviously blown, but were.

I haven't done an all drawn test yet. Also why isn't the fuse blowing, but the relay is?

 

Thanks

1 hour ago, Rotket said:

Also why isn't the fuse blowing, but the relay is?

When You open a blown relay you might see the part that is bad; the coil or the points.  The amp draw test will show the health of the lift pump; a low amp draw is good.  

2 hours ago, IBMobile said:

When You open a blown relay you might see the part that is bad; the coil or the points.  The amp draw test will show the health of the lift pump; a low amp draw is good.  

So just probe the power wire with a tester while the pump is running? Whats good like 3 amp?

You can use a volt-ohm-amp meter that will handle 20 amps in line between the battery and lift pump. 

 

1 hour ago, Rotket said:

Whats good like 3 amp?

Check with the manufacture for amp usage but I would be looking for less than 12 amps.  

Look the pump motor over closely. Both FASS and AirDog have bled holes between the motor and the pump. If the shaft seal fails it should be bleeding fuel out this hole and may drip or keep the base wet with fuel. The pump motor could be full of fuel too.It could be also I've seen a few FASS pump bed side mount and been impact with water, mud, and snow so much the brushes and bearing have taken damage from water and debris intrusion. This could be part of the reason for popping fuses. 

On 2/27/2020 at 9:37 AM, Mopar1973Man said:

Look the pump motor over closely. Both FASS and AirDog have bled holes between the motor and the pump. If the shaft seal fails it should be bleeding fuel out this hole and may drip or keep the base wet with fuel. The pump motor could be full of fuel too.It could be also I've seen a few FASS pump bed side mount and been impact with water, mud, and snow so much the brushes and bearing have taken damage from water and debris intrusion. This could be part of the reason for popping fuses. 

I mean it is pretty old at this point, but its only been on there for 50k miles. It does weep fuel, so maybe it's just fried now?

How long do these pumps usually last, because they're not cheap.

1 hour ago, Rotket said:

I mean it is pretty old at this point, but its only been on there for 50k miles. It does weep fuel, so maybe it's just fried now?

How long do these pumps usually last, because they're not cheap.

I have jad mine for 9 years though the first and second one last 4 years each. This latest is a 4g pump so hopefully it is better, time will tell. Mine were both replaced under warranty all I paid was shipping. You can just replace just the pump. Even the 4g pump fit my base from 9 years ago. Not sure what the pump alone cost. I still believe they both should have lasted a good bit longer than they did. @Mopar1973Man's first last 12 years or more.