Jump to content

97' GMC Sierra K1500 - fuel pump replacement

1997SierraSLT

Recommended Posts

1997SierraSLT Enthusiast

1997SierraSLT

Posted
Posted

Crusing along at 65 mph and romping on the throttle, the truck would fall flat on its face and shudder like crazy. Check engine light would start flashing for about 10 seconds, then it would stay on permantly. The engine would only recover if I back off the throttle, but it still set a hard code. Top speed was about 75 mph if I was lucky without feeling the shuddering effect. This has been happening for years. The dreaded P0300 (random misfire) once again...... Wtih as many articles of discussion pertaining to this diagnostic code, I'm surprised GM doesn't just name a vehicle after it. Honestly, this truck has been spitting out P0300 since the day I bought it with 17K on it.

 

A little history: At 90K miles, I swapped out the OEM SCFI system (poppet valve design) with the new MFI system (injector now located at each cylinder). This seemed to help quite a bit and was a night and day difference over the old design but it still didn't completely solve the problem. At 100K miles replaced plugs, wires, cap and rotor. At 139K miles, I changed out the intake manifold gaskets with the Felpro MS98000T (3rd gasket set total....ridiculous!!). Currently has 140K miles on it.

 

I've read a lot of forums in which the fuel pump should produce 60-66 psi (key on ignition off). Thinking that it may be a weak fuel pump not knowing for sure, I just installed a new Delco HP100001 fuel pump assembly (complete). Wish I would have taken a fuel pressure check on the old pump with key on, ignition off....argh! However, the old pump did hold steady at 50 psi with the engine running. With new pump intalled, I obtain 60 psi (key on, ignition off) which is within spec. With engine running, I'm getting 50 psi which sounds about right with the MFI system. Wish I new exactly what the fuel regulator spec was on the MFI system upgrade. My research has indicated only the CSFI sytems required higher fuel pressures to overcome the spring force of the poppet valve design.

 

Road tested it last night and same thing happened but to a lesser degree. Same symptons and code set as before but the engine recovered much quicker. This time however, it didn't fall flat on it's face. Now it will run up to 85-90 mph. Too bad a hard code is set.

 

Even if a new fuel pump installation didn't completey solve the problem, it did need to be changed out. The strainer at the bottom of the pump was hardended and took little effort to tear it as it had no flexibility left in it. Plus at 140K, it couldn't hurt.

 

Next, I'll check the plugs and wires. If that checks out ok, I'll be road testing it with my buddies laptop hooked up to the OBD-II port using AutoEnginuity scan software to see what is going on with each sensor.

GMstrong Enthusiast

GMstrong

Posted
Posted

That kind of problem can happen to any vehicle.I would have replace the whole sending unit and everything,fuel filter and also the regulator,Did you fix the misfire?Replace your ign module and coil.

1997SierraSLT Enthusiast

1997SierraSLT

Posted
  • Author
Posted

Yes, complete fuel pump assembly was replaced (which includes sending unit). Fuel filter has 5K on it. MFI system which includes regulator has 40K on it. I did a leak down test using a fuel pressure gauge. With key on ignition off, fuel pressure is at 60 psi. When key it turned off, pressure goes to 50 psi and holds steady. I'm quite a ways out from the freeway so I have not done any more testing of the vehicle. No, I have not tested the ignition coil.

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • Grumpy Bear
      OCI, not when but why?

      By Grumpy Bear · Posted

      Sad thing is that this doesn't have to be the case. LSPI can be solved without a reduction in TBN. Swap Ca for Mg.  Cats are not a issue if the OEM can get a ring and valve guide seal even at SN levels of SAPS. Dizzy is purring like a kitten with a bowl of warm milk. 200K of Full SAPS oil and zero detonation issues and nice a clean inside and out. This shouldn't be an issue. It isn't 1920.    Tell ya what AMSOIL SS is excellent at, internal cleanliness. The new formula is even a step up from their already outstanding cleanliness levels. Can't say the OEM offering is quite that clean. There marketing suggest the SS is cleaner.     That is the only defense with at shelf oil. Nothing wrong with them if you ignore the marketing and OEM 'recommended' OCI and use a thimble full of common sense. 😉 You go sir. 
    • StingerZ16
      Roll up bed cover experiences

      By StingerZ16 · Posted

      I started with a folding cover by BAK PAC on my 2500. It went bad after close to 5 years. Bent and vinyl coming loose. Contacted BAK and they gave me a very good discount on a Revolver. Had it a number of years. Mostly outdoor storage. Some garage storage. Vinyl started to come loose. Still under warranty so they replaced to cover. Sold the 2500, bought the 1500 and got another revolver for it. Had it a couple years now and no issues. I store it indoors. Got a bit of discount when buying it as well. If you are seeing problems, contact BAK or real truck and let them know. Customer service was pretty good. But I think they changed their warranty.
    • Chuck FB
      Towing In Loose Gravel

      By Chuck FB · Posted

      I agree, there is no one answer fits all as every rig is different, one may be pulling some little aluminum fishing boat while another is towing a monstrosity that weighs a lot and hopefully the owner if the rig has some prior experience to know what drive mode they should choose.    It also struck me and this is from watching a few of those boat ramp escapades videos in the past, Ford being one of the vehicles that has the auto front axle hubs and sure enough its found out that one hub has crapped out and won't engage and may not have manual hubs to even select on both sides so they are on the boat ramp stuck with no four wheel drive and spinning .... they flat out need a tow to get up the ramp and deal with the vehicles new found issues. That can happen to all brands of pickup, finding out either four wheel drive or 4 low isn't working right at the time its needed it to work as some electronic crap has failed. 
    • Chuck FB
      Towing In Loose Gravel

      By Chuck FB · Posted

      Its possible you never had the joy of the crappy boat launches we tend to have around here or really some of them are just grades down to the river if its a river scenario and the conditions change all the time with the river levels and silt deposits. Some of the lakes we went to years ago, there was no such thing as a cement pad that went down into the water that the trailer stayed on, it was gravel maybe up to the water line and then duck crap much beyond that so sinking the boat tires into mud. Of course some of the more established lakes had a cement bar type boat ramp but sometimes it was covered in green slime closer and certainly within the water and a two wheel drive had all sorts of fun if one had to touch that slime with the rear tires.    A neighbor of mine had made a comment years back with his chev truck that was probably about the same year as yours but a half ton extended cab 4x4 and he a a fiberglass boat with an inboard so it wasn't a feather weight and he had gone out to one of the large popular lakes in the area and don't ask me how this happened but he was in two wheel drive as he figured he didn't require four wheel drive for that boat ramp and somehow upon pulling the boat out he twisted one of his drive axles. I suspect it must have spun and then grabbed on the cement ramp and shocked it to the degree of twisting it. He would have had the standard 8.5 or whatever it was axle housing as the 9.5 ring gear like my truck has also has larger drive axles as far as I know. Anyway he was feeling a vibration driving home and had it checked out and a shop found that the tire/hub was wobbling because of the axle had twisted so in went a new drive axle. After that bad experience he said he made sure to put it into four wheel drive to lower the stress on the rear axle. Of course that is where an HD truck can handle a lot more stress and no doubt these newer half tons with their larger ring gears probably have larger drive axles as well to match vs back in the day. 
    • asilverblazer
      2027 GMC Sierra: Official Discussion

      By asilverblazer · Posted

      Desirable - as in does someone WANT one, aspire to have one. Could reasonably buy any car they want and CHOOSE these instead.    I didn't watch the video, why did they win?

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...