As many may know, I have been chasing a poor driving issue with my truck (from the reading of other posts of mine).

Recently, one of the problems I had was a bad fuel pump. It was replaced, but I wanted to see if the new pump was running properly. I noted I still had a hard start in the morning. I put the pressure tester on it and it charged up to appropriate operating pressure 55-60psi....cannot remember the exact number, but my concern comes in the fact that I left the unit on the truck over night and awoke to a psi reading of 18. Is this normal? Could a vacuum leak cause this drop in pressure, as I believe to have one (my HVAC flapper door is not working properly).

I am at a loss right now......help!!

thanks

 

How much does it leak down in the first 10 minutes? 10 minutes is the only time frame you need to worry about.

 

A vacuum leak has nothing to do with fuel pressure. Trouble with HVAC doors could indicate a vacuum leak in the HVAC/4X4 vacuum system though.

If your vehicle has CSFI, (1996 & newer) pressure needs to be 60psi to 66psi at the service port and 73psi to 108psi capped off at the fuel filter. As 50lb_cat mentioned, it needs to remain above 55psi for at least 10 minutes after the pump shuts off.

 

OK, so I am pretty sure that the fuel pressure is not at issue, seems to hold appropriate pressure....although not 100%, but the truck does have a new fuel pump. Also, I have replaced the following:

MAP sensor
air charge temperature sensor
TPS
IAC
new plugs, wires
new fuel pressure regulator
new fuel filter
4x4 has new transfer case switch
Throttle body has been cleaned

I still feel like there is some restriction however while driving. I also have an intermittent rough idle, but it does seem to run slightly better than before.

HVAC not working (as far as the direction of the air through the vents, but I do have 4 wheel drive)

I really do not know what to think. I did replace the cap and rotor, but I used BWD parts. are these things that finecky that this would have an impact. Also, I was starting to consider the following:

Blocked cat converter (but I do not have any codes showing or CEL's)
cam position sensor
distributor problem

I do not know how to really test for any of these.

any thoughts is appreciated.

thanks

 

What year is your truck?
If applicable, have you cleaned the EGR valve and MAF sensor?

Have you noticed a rotten egg smell from the exhaust? You can also band on the cat, if it rattles and you noticed a smell then the cat is probably bad. You can also take it to a muffler shop and have them check the exhaust pressure.

It is also possible that the gear in the distributor shaft is worn out. I had that problem on my 99.

 

The truck is and '04. I do not notice and smell and the converter does not rattle. I was going to see if the shop could check the exhaust pressure, but was not sure if that was the way to go.

My truck does not seem to have an EGR and I did clean the MAF. (again, no codes)

When I am driving sometimes I do feel like a skip or stutter or mis or whatever you want to call it. The only thing I can think of at this point is something ignition oriented and with everythingI replaced, I am thinking distributor. Any thoughts. How would I check or test this?

Photos?

Thanks

 

Yes, 04 won't have an EGR. I would have the shop check the exhaust pressure first. To my knowledge there is no test of the distributor gears. You have to pull it and its just a visible inspection. You can have a shop with the right scan tool check the retard however. If you pull it be sure to get it lined up correctly.

You mentioned you replaced the plugs and wires are you sure they are seated all the way?

I bought a skip white unit off ebay for 50 bucks. The shaft is turned aluminum. I was impressed with it. It comes with Accell cap and rotor so I swaped them out for delco and it doesn't miss a beat.

 

I double checked the wires and everything was seated correctly, I plan on doing the water mist test on the wires to see if they are jumping spark or arcing.

I did notice that recently, the truck seems to be very shaky at a stop light or or sign.

Another thing I need to check is the new cap and rotor I put on and see if there are any unual things since it was replaced. I did use BWD....not sure if that is an issue.

When you say mark the distributor, can you be a little more clear? just want to make sure I am ok with knowing what I am doing. thanks

 

Yes these things are that finicky when it comes to plugs, cap & rotor. They like AC Delco, anything else is a gamble, and you'll probably lose

If the distributor gear is worn, it's because the distributor shaft bushings are worn excessively and that can/will cause P0300 series DTC's to set along with misfires/rough idle etc etc. As 50lb_cat mentioned, incorrect camshaft retard can also cause similar issues. Checking distributor bushings requires the use of a scope, (expensive piece of equipment) by a qualified technician.

 

https://blazerforum.com/forum/tech-articles-diy-29/edi-engine-timing-24373/

That link should help you out with removal of the dizzy