Truck surging

[john65td]

This problem happens when im crusing around 50mph. the truck will all the sudden just jerk n surge rpm stay constant and if i acellerate it stops the only speed it happens is 45 to 50 never any other time. its not a hard surge but you feel it. a week ago i got some bad fuel so i ran it out and changed the filter and got good fuel. it was falling on its face with the bad fuel. lp and op are bout a year old the lp is working when i did the fuel filter fuel shot up and hit the hood but when i turn the fuel drain tee i get nothing and my oil pressure reads erratic sometimes on the dash. maybe my ops is failing? the fsd is less than a year old mounted on a cooler someone also told me this can be caused by after market locking fuel caps which i have one. any input? thanks john

 

[Matt Bachand]

Sure sounds like it. You want a quality unit there or you'll be replacing it in months to come. Should verify fuel pressure with a gauge, but the oil pressure erratic seems to be you need a new OPS regardless (hopefully), and that runs power to your LP too.

PMDCABLE.COM sells a nice extension for the OPS unit that makes it alot more accessible to change. He sells the OPS's there too. Check it out.

 

[john65td]

Got in my truck yesterday started it up oil pressure pegged at 80psi so went and got a ops replaced it oil pressure reads right now and lp works got fuel at the drain tee and 6 psi fuel pressure so it confirmed it was my ops goin bad truck is up and running normal again

 

[buddy]

You should put a relay to run the LP, triggered by the OPS, that will prevent you from having this problem a year from now, or less.

 

[john65td]

can you give me the info to do that? will it still work the same? that would be great the old ops only lasted me 7 months. thanks

 

[buddy]

are you familiar with relay wiring? They have 4 or 5 contacts. The center one if it has the 5th contact is 87a, not needed right now, so 4 contact would be OK.

To make the OPS the relay trigger.....
Take the grey wire output of the OPS, cut it several inches back from the harness, and connect the OPS harness side to contact 85. You need to be able to work with both sides of the grey wire you cut, so leave enough wire length on each side. You may need to solder or crimp in some additional wire. You can connect wires to the relay with blade crimp terminals. Contact 86 of the relay then needs to be grounded anywhere. This now means the relay will allow voltage/current to pass through from contact 30 to 87 when the OPS would normally power the LP.

To provide the power.....
put battery voltage to contact 30. You can either split it from the orange wire that already provides the power to the OPS or get it from somewhere else. I used a battery junction post on the firewall, used 12 gauge wire, a crimp ring termal to the post, crimp blade to the relay.

To send the power to the LP...
the other side of the grey wire that you cut coming out of the OPS harness goes to the LP, and needs to be connected to contact 87 of the relay. You may need to solder or crimp in some additional wire.


----------------------------------------

You could also do an OPS extension if getting to the stock location annoys you enough. PMDcable.com sells a nice premade extension. I used a grease hose with 1/8" to 1/4" adaptor fittings for each end. The OPS casing/threads need a good engine ground, so I put a terminal ring (and washer because there was space) between the 1/8" grease hose fitting and 1/4" adaptor fitting on OPS side of the grease hose.

 

[john65td]

Thanks buddy ill give that a try