Help!! 03 3.7 V drop at fuel pump

Joeyd900

New Member
Joined
Aug 1, 2021
Messages
6
Reaction score
1
03, auto, after new head gaskets, timing chains/guides,new Cs and Ck sensors, fuel pump/filter, et al, only 7 volts at pump. PDC Fuses and relays good. Jumped fuel pump- its good. No pump prime. Is there a reset switch for asd ?
 

Billwill

Full Access Member
Joined
Nov 26, 2009
Messages
1,973
Reaction score
444
Location
White River, South Africa
Welcome to the Forum!

Download the 2003 Jeep KJ Service Manuals here!

www.colorado4wheel.com/manuals/Jeep/KJ

Section 8W has the Wiring diagrams...the Index will show you that page 8W-30-4 has the Fuel Pump Module for the LHD module.

G320 is the ground point for the Fuel Pump Module which you will find on page 8W-15-18...this is a Black wire (BK).

This G320 is somewhere at the Fuel Tank......you can always add another ground there!

The previous page 8W-30-3 shows how Fuse #24 20 A in the PDC....the fuse/relay box under the hood..feeds +12 volts to the Fuel Pump Module via a Dark Green/White (DG/WT) wire via 3 Connectors...C100, C201 and C307.
You can find the physical location of these Connectors in the Index section. You may have to re-plug these connectors a few times in case of a bad contact!
The Index Section will also show you the locations of the Ground Points.

First thing to check is your main Ground points...after all the work done on the engine there may be a missing or loose ground!

Check the Negative Lead of the Battery Terminal is clean and tight on the battery, check the Positive Lead likewise is clean and tight.

Check the Negative Battery Lead going to Chassis is on clean and tight and there are two braided Ground Straps going from the rear of the heads to the Firewall....make sure these are clean and tight.

Swap out the Fuel Pump Relay with an identical one nearby.

With Ignition ON trace the +12 volts all the way from Fuse number 24 down to the Fuel Pump Module via the DG/WT wire....do this with reference to chassis/engine as your ground and also with reference to the Black wire on the Fuel Pump Module as Ground.

This +12 volts should be there...if not then you have a bad ground or connector pin or a very bad Battery.

Is the Fuel Pump Relay Relay energizing? You can try jumper female pins 30 and 87 together inside the empty socket.
 
Last edited:

Joeyd900

New Member
Joined
Aug 1, 2021
Messages
6
Reaction score
1
Welcome to the Forum!

Download the 2003 Jeep KJ Service Manuals here!

www.colorado4wheel.com/manuals/Jeep/KJ

Section 8W has the Wiring diagrams...the Index will show you that page 8W-30-4 has the Fuel Pump Module for the LHD module.

G320 is the ground point for the Fuel Pump Module which you will find on page 8W-15-18...this is a Black wire (BK).

This G320 is somewhere at the Fuel Tank......you can always add another ground there!

The previous page 8W-30-3 shows how Fuse #24 20 A in the PDC....the fuse/relay box under the hood..feeds +12 volts to the Fuel Pump Module via a Dark Green/White (DG/WT) wire via 3 Connectors...C100, C201 and C307.
You can find the physical location of these Connectors in the Index section. You may have to re-plug these connectors a few times in case of a bad contact!
The Index Section will also show you the locations of the Ground Points.

First thing to check is your main Ground points...after all the work done on the engine there may be a missing or loose ground!

Check the Negative Lead of the Battery Terminal is clean and tight on the battery, check the Positive Lead likewise is clean and tight.

Check the Negative Battery Lead going to Chassis is on clean and tight and there are two braided Ground Straps going from the rear of the heads to the Firewall....make sure these are clean and tight.

Swap out the Fuel Pump Relay with an identical one nearby.

With Ignition ON trace the +12 volts all the way from Fuse number 24 down to the Fuel Pump Module via the DG/WT wire....do this with reference to chassis/engine as your ground and also with reference to the Black wire on the Fuel Pump Module as Ground.

This +12 volts should be there...if not then you have a bad ground or connector pin.

Welcome to the Forum!

Download the 2003 Jeep KJ Service Manuals here!

www.colorado4wheel.com/manuals/Jeep/KJ

Section 8W has the Wiring diagrams...the Index will show you that page 8W-30-4 has the Fuel Pump Module for the LHD module.

G320 is the ground point for the Fuel Pump Module which you will find on page 8W-15-18...this is a Black wire (BK).

This G320 is somewhere at the Fuel Tank......you can always add another ground there!

The previous page 8W-30-3 shows how Fuse #24 20 A in the PDC....the fuse/relay box under the hood..feeds +12 volts to the Fuel Pump Module via a Dark Green/White (DG/WT) wire via 3 Connectors...C100, C201 and C307.
You can find the physical location of these Connectors in the Index section. You may have to re-plug these connectors a few times in case of a bad contact!
The Index Section will also show you the locations of the Ground Points.

First thing to check is your main Ground points...after all the work done on the engine there may be a missing or loose ground!

Check the Negative Lead of the Battery Terminal is clean and tight on the battery, check the Positive Lead likewise is clean and tight.

Check the Negative Battery Lead going to Chassis is on clean and tight and there are two braided Ground Straps going from the rear of the heads to the Firewall....make sure these are clean and tight.

Swap out the Fuel Pump Relay with an identical one nearby.

With Ignition ON trace the +12 volts all the way from Fuse number 24 down to the Fuel Pump Module via the DG/WT wire....do this with reference to chassis/engine as your ground and also with reference to the Black wire on the Fuel Pump Module as Ground.

This +12 volts should be there...if not then you have a bad ground or connector pin or a very bad Battery.

Is the Fuel Pump Relay Relay energizing? You can try jumper female pins 30 and 87 together inside the empty socket.
Ok, so traced DG/WH, ground behind battery loose, figured out only 12v for a second or two at fuel pump. Found a pinch in new fuel filter line, , no pressure at rail. Fixed problem, suddenly 7 new codes up. So, I start with the lowest numerically, Cam sensor failure, hmmm didnt I replace that? NOT FULLY PLUGGED IN, 3 MONTHS LATER ITS A DAGG0NE PLUG. All that to find my replacement head's are bad, leaking into the block, thick white smoke.
Got any ideas on how I can check to make sure the block is still good? I can't imagine that it is cracked as well but, would like to know b4 I invest in new heads. Thanks a ton for your help, I haven't read schematics since my army days (radar technician) aND Im no auto mechanic.
 

Billwill

Full Access Member
Joined
Nov 26, 2009
Messages
1,973
Reaction score
444
Location
White River, South Africa
Glad the electronics seem to be working well now!:)

Sad about the white smoke!o_O

That Dark Green/White wire is not a ground but is the +12 volts going onto the actual Fuel Pump so it having a loose connection would definitely be the cause of the voltage drop there!

I am no expert on the mechanical sides of the engines..maybe best to start a new post about this smoke/bad-heads issue so that the Engine Experts here can see your post and can respond!
 
Last edited:
Top