4l60e 1-2 shift does not happen at WOT

[clinebarger]

Originally Posted by JNJchev77

Well, I changed the PCS out last week and no change!


TPS tested fine but I've read it could still be bad, so I am going to change out TPS and VSS, only because it's cheap and easy... Also, should have access to a programmer to mess with shift points, gear ratio, etc, but want to change the sensors first to see if that helps...

Changing those sensor will not help, The ratio in the tune NEEDS to be corrected FIRST.

[JNJchev77]

Originally Posted by clinebarger

Changing those sensor will not help, The ratio in the tune NEEDS to be corrected FIRST.

I corrected the ratio in the computer to what I actually have in the truck... 3:08's. And there was no change. Post #17

I updated the gear ratio using an aftermarket programmer... Will that update it correctly?

[clinebarger]

Originally Posted by JNJchev77

So I have the computer set up with the correct gears, that are currently 3:08's. Truck is still doing the same thing. At WOT it just stops pulling at about 3,000 rpm but rpm's keep climbing. When I'm cruising at 20-25 or so and got to WOT, same thing... downshifts and about 3K, stops pulling, rpm's keep climbing...

Could it be a TPS issue?

Shifts fine otherwise, at 1/2 throttle. and fine at WOT for 2-3rd....

I guess I did not read this post, A WOT 1-2 shift don't happen 'till past 5,000 rpm, A fueling issue can cause this.

[JNJchev77]

Originally Posted by clinebarger

I guess I did not read this post, A WOT 1-2 shift don't happen 'till past 5,000 rpm, A fueling issue can cause this.

Well, the old fuel pump seemed fine and then started to make a crazy squealing noise about a week ago and the truck bogged down when I gave it any gas, even backfired a time or two. So I just changed the fuel pump, figured it was shot, and fired it up and about a minute or so after idle, it started making the same noise... wtf?! Fuel system clogged somewhere?

I have a pre-filter and filtered in between pump and rails. Same filter each side, trick flow 40 micron filter, walbro 255...

[BR3W CITY]

IMO pre filters clog or cavitate, the only time I run one is the in-tank sock (if I have an in tank). I just run a good filter after the pump, and keep an eye on it. The pump itself can move a good amount of garbage without actually causing a problem. Starving the pump of fuel or restricting it is actually worse than letting it pass some debris.

Was the noise actully coming from the pump? When fluid flow has an air leak, or has air introduced to the system (aeration), or hits an obstruction and cavitates (basically bounces around) it can make a hell of a noise. Shower heads in old homes will do the same thing when the line gets calcified or when pipes werent de-burred.

Take a look at the lines and fittings as well to make sure they are all positively engaged and not pinched, or mis aligned (especially when going from hard line and back). Not fixing it can actually cause the fluid to wear at the line and cause a burst failure.

[JNJchev77]

Originally Posted by BR3W CITY

IMO pre filters clog or cavitate, the only time I run one is the in-tank sock (if I have an in tank). I just run a good filter after the pump, and keep an eye on it. The pump itself can move a good amount of garbage without actually causing a problem. Starving the pump of fuel or restricting it is actually worse than letting it pass some debris.

Was the noise actully coming from the pump? When fluid flow has an air leak, or has air introduced to the system (aeration), or hits an obstruction and cavitates (basically bounces around) it can make a hell of a noise. Shower heads in old homes will do the same thing when the line gets calcified or when pipes werent de-burred.

Take a look at the lines and fittings as well to make sure they are all positively engaged and not pinched, or mis aligned (especially when going from hard line and back). Not fixing it can actually cause the fluid to wear at the line and cause a burst failure.

BR3W, I agree with you on the pre-filter. I just added it when I changed this pump out last night. I added foam to the fuel cell and figured that killed the fuel pump, but the foam was added 8 months ago. The new pump is making the same noise as the old pump... The old pump didn't start to make this noise until last week. Has about 500 miles on it, so I know it's not the pump after changing it out.... I checked for kinks or anything odd and didn't find anything unusual....?

[JNJchev77]

Continuation from last post...

Last week when I did test runs, I took a couple turns and had low fuel in cell and the truck bogged shortly after turn but then picked up. So I figured pump was not getting fuel through turn because of low fuel level... But the next day when I took it out, after the pump started making the high pitched squeal, it bogged down anytime I tried to give it some throttle. (I added about 5 gallons so it wasn't low on fuel).

Could air be in the line and not releasing through return? I haven't checked fuel pressure, guess that would be a good start?

In park if I rev the engine it's smooth, no bogging down? I have always kind of had an issue with starts as sometimes I have to give it a little gas... but checked fuel pressure at first start up and it was at 58psi. That was a year and a half ago...

[BR3W CITY]

Check for FP and throw a meter on the power wire at the pump. Have a friend rev it in neutral. Part of me wonders if the noise if the electric pump motor straining under improper voltage.

I've seen the ghetto-bleed for the lines (pressurize the line, then have someone try to bleed pressure at the schroeder valve). Fire risk tho, so be careful.

[JNJchev77]

Originally Posted by BR3W CITY

Check for FP and throw a meter on the power wire at the pump. Have a friend rev it in neutral. Part of me wonders if the noise if the electric pump motor straining under improper voltage.

I've seen the ghetto-bleed for the lines (pressurize the line, then have someone try to bleed pressure at the schroeder valve). Fire risk tho, so be careful.

I am curious about the voltage too, as the tuner that I was using was running through the fuel pump line at my truck harness and had never made the noise before. Probably not the smartest move, but I'm impatient from time to time lol. But the tuner has been uninstalled as I said. I will check the voltage...

I can handle bleeding it that way. I can do that without the truck running, correct?

[JNJchev77]

Ok... checked the fuel pump and it's pulling 25amps which is just about right. and checked the fuel pressure..... and it's at 48 psi ... My buddy seems to think it's a bad pump but because the previous pump was acting up I think a chunk of foam broke down and traveled through the line to the post pump filter, when fuel level was low.(seeing as I didn't have a pre-filter before)... When I purge the line at the pressure tester I get some air bubbles in the line...

Anyone have an idea? I didn't pull the filter yet, kids took over the night lol...

[clinebarger]

Originally Posted by JNJchev77

Ok... checked the fuel pump and it's pulling 25amps which is just about right. and checked the fuel pressure..... and it's at 48 psi ... My buddy seems to think it's a bad pump but because the previous pump was acting up I think a chunk of foam broke down and traveled through the line to the post pump filter, when fuel level was low.(seeing as I didn't have a pre-filter before)... When I purge the line at the pressure tester I get some air bubbles in the line...

Anyone have an idea? I didn't pull the filter yet, kids took over the night lol...

25 AMPS!!!!!! WOW! That's ridiculous current draw. A spike to 15 AMPS & Steady at 7 AMPS is "about" normal. Bad ground? Restricted fuel system? Other wiring issues?

[JNJchev77]

Well, I'm assuming something in my fuel line is restricting. I thought I read that the amperage for this fuel pump was 25-30? Obviously I read that wrong.

The ground is good. The only wiring issue I could have is the the pump is running through my ezwiring truck harness(fused). I know these harness's are wired a little different but didn't think it would cause an issue.

I'm going to pull the filter between pump and rails to see if something got through and is restricting flow. If nothing is restricting that line I was going to run a separate wire from pump to relay.... Hoping it's something as simple as that.

[JNJchev77]

I pulled the "post pump filter" and found that the screen was completely clogged. Also when I checked the old pump found that there was a lot of small foam pieces and even some of the braided steel line in the pump. Guess I didn't get it cleaned out enough before initial install and I didn't have a pre-filter prior to this...

Put new screen filter in and fuel pressure is right at 58 psi ... Oh and the amp pull is right at 7 amps... It always helps to have it on the right setting, Gotta learn somehow I guess... Anyway, taking it for a test drive today to make sure my fuel issue is solved then I can get back to the shifting issue

Thanks for everyone's help up until this point, I really appreciate it!!

J

[JNJchev77]

Well... for anyone that still cares or may have this problem in the future... It was a fuel issue as Clinebarger hinted. Looks like motor was running lean and just not getting fuel.

Truck pulls hard shifts when supposed to. Now onto changing to 3.73's and work with HP Tuners.

Thanks for the help!

[oldman3]

Glad you got it sorted out...Jim

[JNJchev77]

Thanks Jim!