98 Vortec 7.4L injector/FPR replacement. How bad of a job is it?

wtd

Messages
2,648
Location
southwest Mo.
My 98 K3500 truck has not been starting that great lately after sitting for awhile. Today I hooked a fuel pressure gauge up to the port to see what kind of pressure it had after sitting for a couple of days. It had about 5 psi.

I turned on the key and let the pump prime to see high it would get. It went up to 58 psi and then started dropping slowly. About two hours later we are at 45 psi. I know that these engines have issues with injectors as they get older so I'm assuming that either some of them are leaking or that the FPR is.

I know you have to take off the upper intake to get to them. Has anyone here done this repair before and is there any tricks or procedures to make it easier? I understand that the EGR valve tube can be very difficult to get undone if it comes undone at all. I've been spraying it down occasionally for the past two hours in hopes that it will eventually come apart.

I've watched a couple of YT videos and they make it seem like a not very fun job so I'm not sure I want to tackle it or not. Thanks.
 
Messages
240
Location
Pennsylvania
dropping from 58 to 45 after 2 hours isnt an issue. A leaking fuel pressure regulator or leaking injectors would present as a driveability issue and either would result in fuel pressure dropping to almost zero very rapidly
 

wtd

Thread starter
Messages
2,648
Location
southwest Mo.
dropping from 58 to 45 after 2 hours isnt an issue. A leaking fuel pressure regulator or leaking injectors would present as a driveability issue and either would result in fuel pressure dropping to almost zero very rapidly
Ok. What about the fact that it was only at 5 psi after a few days? Is that normal? I just checked it again and it's been about 4 hrs and 15 minutes and it's down to about 35 psi. I don't see any fuel leakage at the shrader valve where the gauge is hooked up at.

There is not a CEL on so I'm not getting any codes to indicate a rich condition and the tail pipe is still spotless so maybe there is not really a problem. I thought that the fuel system was supposed to stay pressurized though and is why I thought that there might be a problem.

Thanks for your input.
 
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25,454
Location
MA, Mittelfranken.de
The pressure is not a problem, if an injector stuck open you would know it, lots of smoke, oil dilution like crazy. You are correct though the injectors are absolute rubbish on these, these are the Multec 1 by Rochester. The failure rate on these is horrendous, they are not worth servicing just replace them with something more modern.

Put some Bosch Gen III 4 hole injectors ( 0280155884) in there and the engine will come alive with better fuel economy. These are a plug and play replacement for the Multec 1.
 
Messages
240
Location
Pennsylvania
Ok. What about the fact that it was only at 5 psi after a few days? Is that normal? I just checked it again and it's been about 4 hrs and 15 minutes and it's down to about 35 psi. I don't see any fuel leakage at the shrader valve where the gauge is hooked up at.

There is not a CEL on so I'm not getting any codes to indicate a rich condition and the tail pipe is still spotless so maybe there is not really a problem. I thought that the fuel system was supposed to stay pressurized though and is why I thought that there might be a problem.

Thanks for your input.
No, its normal for fuel pressure to drop key off on a port fuel vehicle. This is why when you turn the key on before you start cranking the engine the fuel system will prime for 2 seconds to make sure there is fuel there once you start cranking
 
Messages
5,406
Location
Fort Worth, Texas
The Injectors could be a sticky/restricted when cold & not flow enough fuel for a quick cold start. Like Trav said....The Multec 1 injector are trash & have a tendency to internally Short as well.

You can test the theory by spraying some fuel or carb cleaner in the Intake & see if it's starts faster cold after it sits, You'd think it would suffer performance wise.....But might only be apparent at engine loads approaching 100%.

Might need some heat on the EGR tube nut, I have 12-point Flare Nut "Slugging" wrenches made by Martin just for EGR tube nuts.
 

wtd

Thread starter
Messages
2,648
Location
southwest Mo.
Thanks everyone for your replies. I guess I won't worry about it then. I do plan to upgrade to the Bosch injectors when I do have to replace them. I've had this truck for almost 13 years and read about the crappy stock injectors soon after I got it.

Performance wise, I've not noticed anything off. It still has good power and runs smooth going down the road. At idle it's not too bad either. It just seems to have a little hiccup at startup sometimes. I do run Chevron Techron concentrate in it occasionally and it may be time to do it again. I think it's been awhile.
 

wtd

Thread starter
Messages
2,648
Location
southwest Mo.
Clinebarger, do you happen to have a picture of the 12 point flare nut "slugging" wrench you are talking about. Is it a 1 3/8" size? Thanks.
 
Messages
25,454
Location
MA, Mittelfranken.de
Thanks everyone for your replies. I guess I won't worry about it then. I do plan to upgrade to the Bosch injectors when I do have to replace them. I've had this truck for almost 13 years and read about the crappy stock injectors soon after I got it.

Performance wise, I've not noticed anything off. It still has good power and runs smooth going down the road. At idle it's not too bad either. It just seems to have a little hiccup at startup sometimes. I do run Chevron Techron concentrate in it occasionally and it may be time to do it again. I think it's been awhile.

If its running okay forget it, dont try and have the original injectors cleaned, cleaning them can and usually does kill off one or more. I don't even take them in anymore. Try some Redline SI-1 in it, use a full bottle for a full tank, then run a can of Berrymans Chemtool, the combination will address both deposits and varnish.
 

wtd

Thread starter
Messages
2,648
Location
southwest Mo.
If its running okay forget it, dont try and have the original injectors cleaned, cleaning them can and usually does kill off one or more. I don't even take them in anymore. Try some Redline SI-1 in it, use a full bottle for a full tank, then run a can of Berrymans Chemtool, the combination will address both deposits and varnish.
Ok, thanks. I will try that. I wasn't planning on trying to remove the originals to get cleaned. If I do the job to get to them, they are being replaced with the better Bosch ones. The truck only has 119,000 miles on it so maybe the original ones will last awhile longer.
 
Messages
5,406
Location
Fort Worth, Texas
Clinebarger, do you happen to have a picture of the 12 point flare nut "slugging" wrench you are talking about. Is it a 1 3/8" size? Thanks.


Here you go......I didn't take a pic of the 1-3/8" one but the Martin part# is 4144. It's a lot shorter than a standard wrench which makes positioning it to strike it a lot easier.

The hex end is very wide which allows it to grab more surface area of the nut.

3jIsIsJ.jpg
 

wtd

Thread starter
Messages
2,648
Location
southwest Mo.
Here you go......I didn't take a pic of the 1-3/8" one but the Martin part# is 4144. It's a lot shorter than a standard wrench which makes positioning it to strike it a lot easier.

The hex end is very wide which allows it to grab more surface area of the nut.

3jIsIsJ.jpg
Thank you for the picture and part #. I will see about picking one up for when I do need to do this job so I can be prepared.
 
Messages
1,598
Location
Ohio
My 98 K3500 truck has not been starting that great lately after sitting for awhile. Today I hooked a fuel pressure gauge up to the port to see what kind of pressure it had after sitting for a couple of days. It had about 5 psi.

I turned on the key and let the pump prime to see high it would get. It went up to 58 psi and then started dropping slowly. About two hours later we are at 45 psi. I know that these engines have issues with injectors as they get older so I'm assuming that either some of them are leaking or that the FPR is.

Have you checked the fuel lines, especially back near the tank? I had the same issue with my 99 K2500, turned out to be rusty fuel line with a very small leak.

I know you have to take off the upper intake to get to them. Has anyone here done this repair before and is there any tricks or procedures to make it easier? I understand that the EGR valve tube can be very difficult to get undone if it comes undone at all. I've been spraying it down occasionally for the past two hours in hopes that it will eventually come apart.

I've watched a couple of YT videos and they make it seem like a not very fun job so I'm not sure I want to tackle it or not. Thanks.

I used a little heat and and two 18" crescent wrenches, came off pretty easy.

Also this:

The pressure is not a problem, if an injector stuck open you would know it, lots of smoke, oil dilution like crazy. You are correct though the injectors are absolute rubbish on these, these are the Multec 1 by Rochester. The failure rate on these is horrendous, they are not worth servicing just replace them with something more modern.

Put some Bosch Gen III 4 hole injectors ( 0280155884) in there and the engine will come alive with better fuel economy. These are a plug and play replacement for the Multec 1.
 

wtd

Thread starter
Messages
2,648
Location
southwest Mo.
Have you checked the fuel lines, especially back near the tank? I had the same issue with my 99 K2500, turned out to be rusty fuel line with a very small leak.



I used a little heat and and two 18" crescent wrenches, came off pretty easy.

Also this:
I will check the fuel lines. I've already had to replace a brake line back there since it rusted and developed a hole.

I plan on updating the fuel injectors to the Bosch ones at some point. Thanks for the info.
 
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