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I'm confused about a situation with the fuel pump on my 98…

Customer Question
Hi Pearl, I'm confused...

Hi Pearl, I'm confused about a situation with the fuel pump on my 98 Silverado. The factory pump setup has a square plug and 4 pin oval plug setup. The pump I ordered (was supposed to be an oem replacement) has a square plug and a smaller 3 pin oval plug setup. I'm trying to find a connector that I can wire in to get the truck to the 3 pin setup (since I've already installed the pump) but all I'm able to find is the harness that would take a 3 pin to a 4 pin. I also tried to source another pump, but they all seem to have a different setup than my truck has. Do you know where I could source the harness I'm looking for?

Mechanic's Assistant: Okay, I'll connect you to the mechanic to help find that for your Chevrolet Silverado. Before I do, is there anything else you want him to know?

I don't think so....... :)

Submitted: 4 months ago.Category: Chevy
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Answered in 2 minutes by:
11/28/2017
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago
George H.
George H., ASE Certified Technician
Category: Chevy
Satisfied Customers: 19,156
Experience: GM Tech ASE Master Tech 15+ years
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Hello I will help,

They changed the connector, did you not get one with the pump? What is the brand and part number of the pump you have?

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Customer reply replied 4 months ago
I didn't get the connector with the pump. Its a bosch (was ordered through rockauto) so I went back to their site and looked at other brands of pumps, but they supply only the connector to convert it to the wide oval 4 pin or square, not the small 3 pin connector I'm hoping to find
Customer reply replied 4 months ago
the bosch part number is *****
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

Ok, do you know the number from the top of your old pump or have access to the RPO code list in the glove box?

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Customer reply replied 4 months ago
or 25314321
Customer reply replied 4 months ago
its a 98 chev k1500 last 8 digits of the serial number is *****
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

The serial number does me no good. If you don't have access to the codes I will have several questions about options.

A couple are 4wd?

Tank size?

I suspect the pump is incorrect for your emissions but I can check if you can supply the information.

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Customer reply replied 4 months ago
It is a 4wd correct. The tank size is 20 gallon (I think its a 90L tank)
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

Is it only the pressure sensor that is not fitting?

Which engine is in the truck?

The pump connector from oval to square is correct or are you short pins?

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Customer reply replied 4 months ago
The 4 pin square shaped connector fits properly. Its the oval 4 pin connector that is on the truck that needs to be changed to the oval 3 pin that is the issue.
Customer reply replied 4 months ago
the engine is a 5.7L
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

This is only the pump connector not the pressure sensor connector right?

What wire colors are you seeing at the truck connector? Purple, black, grey and?

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Customer reply replied 4 months ago
I'm sorry, I don't know which is the pump connector vs the pressure connector. I have pictures of the connectors, but can't tell the color of the wires (and the truck isn't here with me now). If you need that info, I'll have to go out to the truck and reply a little later.
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

There is the square pump connector that should have a white shell and a black sensor that is clipped onto the top of the pump housing. The black sensor has 3 wires, the pump connector has 4. Your old pump connector was a flat 4 pin oval and they provided an adapter with the pump that goes from the flat 4 to the square and plugs into the pump?

Is all that correct?

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Customer reply replied 4 months ago
that summary is correct, but no wiring adaptor was provided. That is what I'm trying to find.
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

OK, I was not understanding the 3 - 4 conversion you asked about. Take a look at this adapter (click here) and see if that is what will fit. They should have included it with the pump.

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Customer reply replied 4 months ago
we're getting closer, lol, thank you for your patience! The adaptor you provided the link for converts the flat 4 pin to the square 4 pin. I need to convert the flat 4 pin to the flat 3 pin
Customer reply replied 4 months ago
http://www.rockauto.com/en/moreinfo.php?pk=976979&cc=1303614&jsn=468 this is the pump that I have installed if it helps with the description
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

This (Click) could also be used but I would need you to check you connector wire colors so I could be sure of what you need to solder to what color on the adapter to get it correct

The flat 3 pin for the black sensor connection?

You have an oval 4 pin with heavy wires on your truck and that plugs into the first adapter I posted, then the adapter plugs into the square connector on the pump. Has to be a 4 to 4 connection.

The sensor on the pump has an oval 3 pin connector. Does your truck have a smaller connector that will match that. It is not the one with heavy wires, these are much thinner.

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Customer reply replied 4 months ago
is it possible to email you the pics I have? I'm now starting to wonder if the harness has been changed away from factory by a former owner, because the description isn't making sense (which would also explain why I can't find the adaptor I'm looking for)
Customer reply replied 4 months ago
I would have to go to the truck to confirm the wiring colors as well
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

There is a paperclip icon or an "add files" button that allows you to attach pictures. Email does not work with the way this site is setup.

Pictures will certainly help, if you find the 3 pin emission connector that should have been plugged into the sensor on top of the old pump then it should have black, dark green and grey wires connected to it.

Let me know how I can help, I am here for the next 5 hours or so. Don't rush but make sure you post back to this thread so I am notified.

Thanks

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Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

If you check that connector you will find it fits the old pump. It is not for that pressure sensor you are trying to connect it to. There should be another connector somewhere for the sensor. It might be tucked up somewhere.

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Customer reply replied 4 months ago
ohhhhhhh that would make sense. I'll take a look.
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

That connector (4pin) is what you plug the adapter cable into and the other end will fit the square connector

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Customer reply replied 4 months ago
ok I'll take a look for the other connector. so in theory (if there is another connector as part of the factory harness) I shouldn't require any adaptors correct?
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

No, you need an adapter to get from your oval 4 pin on your truck to the square 4 pin on the pump. The first connector I linked at Summit will fit. Pretty sure your local parts store would have one.

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Customer reply replied 4 months ago
ok, where does the square 4 pin harness plug in?
Customer reply replied 4 months ago
that exists on the factory harness I mean
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

Do you have one on your truck? If you do look to see if it was spliced into the harness. Probably was. Sounds like someone has replaced the pump before, the change was made in the early 2000's

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Customer reply replied 4 months ago
there is a white square 4 pin connector currently on the harness
Customer reply replied 4 months ago
it plugs into the pump, which leaves the oval 4 pin connector that won't plug into the smaller 3 pin that's on the pump :) my apologies for the confusion
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

Then you don't need an adapter, someone has added that in the past. You want to check their work and see it is soldered and has a good connection

The oval connector was for the original pump. It will not be used

Link to diagram

That is what you are looking for to plug into the black pressure sensor

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Customer reply replied 4 months ago
ok sounds good thank you. do you know where I could find one?
Customer reply replied 4 months ago
or tell me what its called so I could search for it?
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

It is just a three pin GM pressure sensor connector. You have the same one on the MAP sensor on the engine. Same sensor as well.

Look around for cut wires or the connector pushed up into a corner above the tank. Are the emission hoses on the canister? One connects to the pump so you can follow that to the canister. I can't find a diagram but I think the wiring comes along that hose. Been a long time since I did one of these. If they got creative and "Improved" things by cutting the emission controls out it won't do you any good to have the connector. The wiring has to run back to the computer.

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Customer reply replied 4 months ago
ok great, I'll take a look for that. Thanks for the help George.
Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

Always glad to help, let me know how I can.

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Chevy Mechanic: George H., ASE Certified Technician replied 4 months ago

Were you able to get this sorted out? Do you need further help?

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