Fuel pump / hotwire problem

[jsta6]

Long time in between posts for me...

Bad fuel pump?

Fuel pump is Reds XP, approximately 12 years old.

Car was acting up.
Car would stall while driving when coming to a stop.
Car would stall when making left hand turn.
Car is fine when making right hand turn.

I checked things out and the relay (Hella 40amp) for the hot wire kit was clicking on and off. I replaced the relay and the problem went away, but then the problem came back a few days later.

When I remove the relay and power the pump directly from the factory fuel pump wire, there are no problems.

Volt meter shows the voltage going up / down when the relay is clicking on and off...

 

[SHADOWII]

Welcome back! I've never looked at my hot wire kit, so take this for what it's worth. First have you ck'd for any thrown codes?
2/ the relay is new, and the problem is repeating, ck the relay coil circuit. What feeds that coil? Don't forget to ck for loose or broken wire/s while inspecting. Maybe put your voltmeter across the coil terminals so you can observe the operation, then work your way back to the source.
Someone more familiar w/the circuit will be able to direct you to the source. If you have a casper's h/wire kit, John might have the schematic on his site. It's worth the look.

 

[jsta6]

Thanks for your reply.

No codes.

Hot wire kit is my own. Hella 40amp weather sealed relay. Power comes from distribution block in trunk (used for stereo amps). No problem there. Ground is OK.

Wires are OK.

I removed the Hella relay from the equation, and ran with the factory relay for about 5 days, then that went. Sigh.

I ran the pump directly off of 12v+ to limp home...

 

[SHADOWII]

That sounds like a possible short in one of the wires or pump itself. Due to a great deal of handling, some times the wires can break inside the protective jack and will act as a heater due to high resistance at the break, which is the opposite of the short, causing low voltage to the unit. Did you check to see if anything got hot when you arrived home after the direct wire hook up?

 

[jsta6]

Wires were not hot. But that doesn't mean much. Could be moving around.

I think I have to drop the tank...I just filled up...lol....

 

[jsta6]

oh, just found this on gnttype:

check the oil pressure switch for leaks or maybe shorting out internally and maybe a shorted wiring harness rubbing against the block

 

[SHADOWII]

That's a possibility, being the age of these tr's.I had a problem w/one of mine w/in 2 yrs of the car being new.

 

[jsta6]

Thanks.

Query:

1. I can't find the in (PNK/BLK) or the out (GRY) of the factory engine oil pressure switch. The engine is covered in 160k miles of grime, and I have a VDO oil pressure sender. Could the wires just be encased in grime or obscured by the VDO sender? or does the VDO oil pressure sender replace the factory engine oil pressure switch? (I don't remember). There is no "OIL" light when key is on.

2. (assuming the TAN/WHT wire going to the fuel pump is disconnected from the fuel pump relay), should the TAN/WHT wire going to the fuel pump be a good source for "ground"? Meaning, if a multimeter is connected to battery 12v+ and is connected to TAN/WHT wire going to fuel pump, should it show 12v or not?

Thanks again.

FYI, for the posterity of future readers, if the fuel pump relay fails, the fuel pump can still get power from the factory engine oil pressure switch, (if there is enough pressure). The factory engine oil pressure switch and the fuel pump relay are on the same fuse, FP/INJ, PNK/BLK. They both have grey wires going to the TAN/WHT wire of the fuel pump. These grey wires are also connected to the "fuel pump prime connector" behind the alternator.

 

[TexasT]

image post


how to capture screen

Mine was leaking like a sieve. See the pin movement? I had a no start so replacing it killed two birds with one stone. I also had to put a new relay on the fender.

 

[jsta6]

But where exactly is it located? And does the vdo sensor replace the OEM sensor?

Fyi, I pulled the fuel pump relay, jumped my fuel pump hot wire to get it to run, cranked it, and probed the grey wire, which should have gotten 12v+ from the engine oil pressure switch, and i got nothing...

 

[TexasT]

I have a tee in mine for my autometer gauge. The front passenger side of the engine block under the turbo right behind the radiator hose. I found this socket to be quite handy.


free image upload

Hard to know if yours was replaced with the sender for an aftermarket gauge or tee'd like I did. You will have to look.
Post a pic maybe someone will be able to see.

 

[jsta6]

Thanks Texas.

It looks like my stock oil pressure switch was removed when the VDO sender was installed.

Unrelated to this problem, I want to put the stock sender back for both the OIL light and the fuel pump connection.

So, I guess I will need a T, and a stock oil pressure switch.

Do you have a pic of the connectors / wires that went on the stock oil pressure switch?

I can only see two prongs in the picture. The stock oil pressure switch has three prongs, correct?

PNK/BLK - 12v+ from FP/INJ fuse
TAN - signal to OIL light (4 psi?)
GRY - to fuel pump prime connector

Also, stock sender is what thread? 1/4" -18 NPT?

The VDO sender 36003 is 1/8"-27 NPT

 

[TexasT]

I'll have to take some pix of my setup. Yes stock is three prongs. The two pix I posted was to show that the prongs moved around a lot and it was leaking like a sieve. I obtained a brass short nipple, a brass tee and more recently when I changed a head gasket put a copper line on from the tee to the gauge to replace the 20yr old plastic. I was not comfortable with the plastic line as old as it was. I also bought a length of black vacuum hose and threaded the copper line through it to kind of hide it through the engine compartment.
I oriented the tee to where the pressure switch points toward the front, the gauge line to the back and the leg into the short nipple and into the block.
You might be able to source a tee with different threads but I'm not sure what the stock threads are. I bought the new bw brand switch from orielly auto parts for like $7.99.
I'll try to remember to take some pix and post em tommorrow. We are out of town at the moment as one of my bil has contracted brain cancer and is in hospice.

 

[jsta6]

oh man, sorry to hear that.

Prayers.

 

[TexasT]

Had a crazy twist to the story. It seems now my mother in law had a stroke so now we are down at the hospital with her. It just keeps getting crazier. I guess her son having probs put too much stress on her. I will get some pix up when I can. Thanks for understanding.

 

[jsta6]

oh my. Please don't worry about the pics.

Prayers.

 

[jsta6]

Update.

I ran the car off of the OEM fuel pump relay. I noticed the voltage would briefly fluctuate between 6 and 12 volts. It ran fine for some short trips.

I then put my 40amp Hella relay / hotwire back on, and it again is running OK. I have not had a chance to measure the voltage yet.

I was going to order a new pump, but I will hold off as I don't want to just start throwing parts at it with money that I don't have...

One thing I noticed is that the fuel gauge now reads about 2/3 more than what it actually is, where before, it would read about 1/3 more than it actually was (been doing this for years).

 

[SHADOWII]

Rich, Sorry to hear about the health issues. I will be praying for them.
Shaun, the drop to 6v's sounds like a damaged or near broke wire. At 6v the current rise must be high. Can you put a fuel pressure gauge on the car and tape it to the windshield so you can monitor it? If you have to pull the pump assy. out you should be able to adjust the sending unit then.
I'll check the schematic to see where the leads go from the oil sensor and get back to you.

 

[SHADOWII]

My manual is showing pink/black to A pin, B-ground, and grey to C-pin on the switch.(which it shows going to fuel pump)

 

[jsta6]

Thanks shadow. I have the FSM and several other schematics.

I ran 12v+ straight to the pump, no problems.

I ran off of the factory fuel pump relay, no problems.

I ran off of my fuel pump hotwire, no problems.

So far, so good. I jiggled all the applicable wires in the engine compartment, the connector by the fuse panel / firewall, the trunk, and the gas tank. No problems.

I ran a wire from the grey fuel pump prime wire (that is behind the alternator) inside the car so that i can monitor the voltage with a multimeter. So far, no problems.

I will continue to monitor.

I DO want to put the OEM oil pressure sender back. I need to buy a new sender, and locate an old or new connector. (part numbers below)

I believe the OEM oil pressure sender is 1/4"-18NPT.

The VDO oil pressure sender that I have (360-003), is 1/8" -27NPT.

I can only ASSume that there is a 1/8" -27NPT to 1/4"-18NPT adapter on there now. (I can't see it).

So, I should only need a 1/4"-18NPT "T" fitting.

FYI, if anyone needs to know, VDO 360-005 oil pressure sender has the 1/4"-18NPT size.
and
GM has a special tool to remove the OEM oil pressure sender. OR, you can use vicegrips / channnel locks or a 26mm 12 point deep socket, OR maybe a 1 1/16" socket.


Cheers!


AC Delco:
Oil Pressure Switch 25036378
Oil Pressure Switch Molded Connector 12085529
(has 3 white wires which need to be spliced in)


Cross reference from Rock auto dot com (ac delco dot com is also an excellent source, and it provides a list of all the vehicles that it was used on)
Oil Pressure Switch 25036378:
BWD/NIEHOFF Part # DR135N
KEMPARTS Part # PS76
AIRTEX / WELLS Part # 9M2
STANDARD MOTOR PRODUCTS Part # PS140T
STANDARD MOTOR PRODUCTS Part # PS140
Alternate/OEM Part Number(s): 10023681, 1254383, 1608288, 1623576, 25036276, 25036375, 25036378, 3241717, 4397891, 6464144, D1803, D1804, D1816, SWG1585
AIRTEX / WELLS Part # 1S6551
Alternate/OEM Part Number(s): 10023681, 12326969, 1254383, 1608288, 1623567, 1623576, 25036276, 25036376, 25036378, 3241717, 4397891, 4397891AB, 6464144, E0AZ9278B, J3241717, PS118


Oil Pressure Switch Molded Connector 12085529 :
ACDELCO Part # PT139
Alternate/OEM Part Number(s): 12085529
STANDARD MOTOR PRODUCTS Part # S956