Fuel Leak Near Engine on M998

[mbeck12]

Hi all, first time writing in here. It's nice to connect.

I've got an '88 M998 and noticed that fuel was leaking towards the front of the vehicle below the engine. Upon a few inspections, it appears that the leak is originating from the the fuel pump. I've attached a few photos, and included a link to a video, to show you what I'm experiencing:

1. Image 1 is above the fuel pump before starting
2. Image 2 is above the fuel pump after starting
3. Image 3 is a close up of Image 2

Here's a video below the fuel pump as the vehicle was running: https://photos.app.goo.gl/bXnSxQeF7SgpZDpe9

As you can see in Images 2 and 3, there's definitely evidence of a leak on the top, but the video shows how much it's leaking from the pump.

I was wondering if anyone has experienced the same, and if so, how you resolved the issue. Any advice is helpful. Thanks much!

 

[Hummer Guy]

Hi all, first time writing in here. It's nice to connect.

I've got an '88 M998 and noticed that fuel was leaking towards the front of the vehicle below the engine. Upon a few inspections, it appears that the leak is originating from the the fuel pump. I've attached a few photos, and included a link to a video, to show you what I'm experiencing:

1. Image 1 is above the fuel pump before starting
2. Image 2 is above the fuel pump after starting
3. Image 3 is a close up of Image 2

Here's a video below the fuel pump as the vehicle was running: https://photos.app.goo.gl/bXnSxQeF7SgpZDpe9

As you can see in Images 2 and 3, there's definitely evidence of a leak on the top, but the video shows how much it's leaking from the pump.

I was wondering if anyone has experienced the same, and if so, how you resolved the issue. Any advice is helpful. Thanks much!

Make sure all of your hoses are tight and not dry rotted. I had a leak at the fuel filter, which was due to a loose line, all I had to do was tighten it.

 

[Mogman]

Looks like a bad pump, very common.
when you replace it you must pull the plate directly behind the pump, use some thick grease on the pump rod and re-insert it, put the plate back on then the pump, use the pump bolts to help align the plate before tightening the two smaller bolts.
Otherwise the pump rod will slide down and you will break it when you install the pump.

 

[Mullaney]

Hi all, first time writing in here. It's nice to connect.

I've got an '88 M998 and noticed that fuel was leaking towards the front of the vehicle below the engine. Upon a few inspections, it appears that the leak is originating from the the fuel pump. I've attached a few photos, and included a link to a video, to show you what I'm experiencing:

1. Image 1 is above the fuel pump before starting
2. Image 2 is above the fuel pump after starting
3. Image 3 is a close up of Image 2

Here's a video below the fuel pump as the vehicle was running: https://photos.app.goo.gl/bXnSxQeF7SgpZDpe9

As you can see in Images 2 and 3, there's definitely evidence of a leak on the top, but the video shows how much it's leaking from the pump.

I was wondering if anyone has experienced the same, and if so, how you resolved the issue. Any advice is helpful. Thanks much!

.
Welcome to the Outfit!

Guess that you were a recent winner on an auction truck? Seems that there have been quite a few of them drifting out the military doors lately... Be sure to download and peruse the TM's (Technical Manuals) for your New-To-You truck. It is so tempting to jump behind the wheel and go for a spin. Take your time, download and at least skim through the books, and give serious consideration to draining and replacing the fluids. When you buy fuel filters - get an extra set. When you are out on the side of the road and the pump isn't pushing "GoGo Juice" a quick swap of fuel filters will bring you back to life more often than not.
KNOWING that you have new clean filters will help you when things don't seem to be going right.

Like @Hummer Guy suggested - Check every hose on the truck. Fuel hoses are held on with a barbed fitting and a crummy clamp. They tend to split when sitting out in the weather and the sun is murder. You won't spend more than a hundred bucks to replace all of them with a bulk roll (cut to length yourself). The hose from the filler to the tank is another spot to look at. They tend to get loose over time. Tightening the clamps is cheap insurance.

@Mogman 's suggestion about the fuel pump is a good one too. If you know what he means - if not - ask questions. Short version of that is that the fuel pump is a lot like a small block Chevy gas engine. The rod that rides on the cam shaft is what makes the pump push gas (Fuel in this case). The grease that you put on it holds it UP in place to replace the pump.

AGAIN, looking in the TM's you will find a picture of the fuel pump and how it attaches to the engine. A picture is worth a thousand words. Use "search" and look at the TM's on a PC rather than trying to see on a phone. Bigger is Better!

Again, welcome to the group - and since we are Picture Hounds, you should maybe create yourself a new thread for your truck and post a few pictures. That way you will have a history of "how it was" and later as you upgrade it here and there - some "how it is now" images. Hope to see it soon...

 

[papakb]

Repost from 2017:

I just did this job on a friends HMMWV and there's no good way to push the fuel pump actuator pin back up into the block without removing the mounting plate. The gaskets are readily available and fit 1955 thru 1995 GM engines and only cost a few bucks so bite the bullet and remove the plate. I used wheel bearing grease to hold the pin up in the block when I remounted the plate and it washes out after the engine warms up so it won't cause any problems down the line. Use a touch of Permatex Hi-Tack to hold the gaskets in place.

A word of advice when you do this job, remove the right splash panel and have a long extension with either a 3/8 swivel socket or a universal with a 3/8 socket to put things back together. This allows you to tighten everything up reaching in over the frame rather than busting your knuckles on all the solid stuff in the neighborhood.

Gasket mounting plate to block: FEL-PRO 5182

Fuel pump: Spectra Premium SP1143MP

Pushrod: Carter PR4 or Dorman 03875

You can pay a whole lot more for the same fuel pump from various vendors online and around town but there's no reason to.

 

[Maxjeep1]

Pump should not show the spring. I just ordered this one from HPG. The one that came off had a lot of free travel before you got to the pumping part.

 

[juanprado]

different vendor made those 2 pumps that is why the spring is different and part of the difference is also the arm but it only rides on the very end.

 

[mbeck12]

Make sure all of your hoses are tight and not dry rotted. I had a leak at the fuel filter, which was due to a loose line, all I had to do was tighten it.

Thanks for the reply and guidance. I'll inspect the lines next and make sure they are all tight and not dry rotted. I did notice a line going into the pump from the top that did appear to be loose, so I tightened the hose clamp, but I'll do some more checking.

 

[mbeck12]

Looks like a bad pump, very common.
when you replace it you must pull the plate directly behind the pump, use some thick grease on the pump rod and re-insert it, put the plate back on then the pump, use the pump bolts to help align the plate before tightening the two smaller bolts.
Otherwise the pump rod will slide down and you will break it when you install the pump.

Thanks for the reply and I appreciate the insight. I'll do some more investigation before I dive in and order a new one. I took notes of your suggestion to avoid breaking anything while installing the pump.

 

[mbeck12]

.
Welcome to the Outfit!

Guess that you were a recent winner on an auction truck? Seems that there have been quite a few of them drifting out the military doors lately... Be sure to download and peruse the TM's (Technical Manuals) for your New-To-You truck. It is so tempting to jump behind the wheel and go for a spin. Take your time, download and at least skim through the books, and give serious consideration to draining and replacing the fluids. WHen you buy fuel filters - get an extra set. When you are out on the side of the road and the pump isn't pushing "GoGo Juice" a quick swap of fuel filters will bring you back to life more often than not.
KNOWING that you have new clean filters will help you when things don't seem to be going right.

Like @Hummer Guy suggested - Check every hose on the truck. Fuel hoses are held on with a barbed fitting and a crummy clamp. They tend to split when sitting out in the weather and the sun is murder. You won't spend more than a hundred bucks to replace all of them with a bulk roll (cut to length yourself). The hose from the filler to the tank is another spot to look at. They tend to get loose over time. Tightening the clamps is cheap insurance.

@Mogman 's suggestion about the fuel pump is a good one too. If you know what he means - if not - ask questions. Short version of that is that the fuel pump is a lot like a small block Chevy gas engine. The rod that rides on the cam shaft is what makes the pump push gas (Fuel in this case). The grease that you put on it holds it UP in place to replace the pump.

AGAIN, looking in the TM's you will find a picture of the fuel pump and how it attaches to the engine. A picture is worth a thousand words. Use "search" and look at the TM's on a PC rather than trying to see on a phone. Bigger is Better!

Again, welcome to the group - and since we are Picture Hounds, you should maybe create yourself a new thread for your truck and post a few pictures. That way you will have a history of "how it was" and later as you upgrade it here and there - some "how it is now" images. Hope to see it soon...

Hey @Mullaney, thanks a lot for the detailed insights. It's great to be part of the Outfit. You all and the forum has been a great resource so far.

We purchased the truck a few years ago from someone who was indeed a winner on an auction truck. I've always wanted one and thrilled to have it.

As for the TMs, I went ahead and located those on the site and downloaded them for future reference. Thanks for pointing me to those.

We have drained and replaced the fluids semi-recently, but the truck has been sitting for a bit and needs some love and general maintenance.

Thanks for your suggestion on buying the extra set of fuel filters, and your guidance related to the hoses, clamps, and fuel pump. I'll definitely keep you all posted as I dive in. I hope it's sooner rather than later.

Lastly, I'll be sure to post some images of the truck for all to see. Thanks again.

 

[mbeck12]

Repost from 2017:

I just did this job on a friends HMMWV and there's no good way to push the fuel pump actuator pin back up into the block without removing the mounting plate. The gaskets are readily available and fit 1955 thru 1995 GM engines and only cost a few bucks so bite the bullet and remove the plate. I used wheel bearing grease to hold the pin up in the block when I remounted the plate and it washes out after the engine warms up so it won't cause any problems down the line. Use a touch of Permatex Hi-Tack to hold the gaskets in place.

A word of advice when you do this job, remove the right splash panel and have a long extension with either a 3/8 swivel socket or a universal with a 3/8 socket to put things back together. This allows you to tighten everything up reaching in over the frame rather than busting your knuckles on all the solid stuff in the neighborhood.

Gasket mounting plate to block: FEL-PRO 5182

Fuel pump: Spectra Premium SP1143MP

Pushrod: Carter PR4 or Dorman 03875

You can pay a whole lot more for the same fuel pump from various vendors online and around town but there's no reason to.

View attachment 877846

Hey @papakb, thanks for all the info here. I'll keep you posted once I dive back in the truck and continue poking around. It seems like a tricky install, but you all have given me a ton of guidance.

 

[mbeck12]

Pump should not show the spring. I just ordered this one from HPG. The one that came off had a lot of free travel before you got to the pumping part.
View attachment 877874View attachment 877875

Hey @Maxjeep1, noted. Will look out for this when I order one. Thanks.

 

[mbeck12]

Hey guys, I just wanted to let you know that replacing the fuel pump fixed the issue. Thank you all for providing great advice and guidance!