96 No Start/ mechanical fuel pump questions

[UPST8NY]

Hi guys,

Need some help here.
1 I recently had engine out to change oil pan.
2 Replaced both steel fuel lines on engine
3 replaced all small fuel lines at pump with correct hose
4 replaced metal line set from back of pump to back of heads
5 replaced cps
6 replaced 1 flex fuel line from engine steel lines to frame lines

Got everything back together and started right up(a couple of revs and it fired right off...I was very suprised)

I started it a few times moving it in and out of garage( It was fine)

when I went to go for a ride it started to lose power gradually to the point it would not run and now not start.

Scanned it ,came up with p4070 exhaust backpressure sensor.
buzz test was fine

[SMKSTAX]

It could be a lot of the things your fuel pump being one of them. An easy check is to look at your engine bay fuse box. Sometimes the fuel heater will short out and cause the #22 fuse to blow. Your PCM is on this same fuse. Another tell-tale sign this is your problem is you will have no wait to start light. Unfortunately their are a lot of other possibilities too.

[balzer_brett]

Mine just lost power and died the other day sounds like it is the same circumstances.. The fix to mine was the exhaust backpressure sensor was plugged, i just took a pick and cleaned mine out that fixed it. i would try that. good luck

[UPST8NY]

Thanks for the replies guys

Fuse 22 is good, as well as all others

Wait to start comes on and goes out normally

Just checked fuel pressure while cranking and had nothing( It looks like I should have 20 psi at 100rpm )

also had fuel filter drain open and cranked engine and did not get any fuel,Although there is fuel in the housing

Im going to throw a new pump at it tommorrow and see where that gets me.(certainly wish I had done this while engine was sitting on the floor)

I will let you know how I make out

Where is the exhaust back pressure sensor located? would changing from squish pipe,cat,and muffler to 3" downmpipe to 4" straight exhaust have anything to do with this code?

[TexasR.N.]

Originally Posted by UPST8NY

certainly wish I had done this while engine was sitting on the floor

Man I know that is right. Let us know what happens. As far as the down pipe and all, I don't believe that it would cause the code. I base this on the fact that I removed all of my factory exhaust and went with a 3" DP and straight pipe out the side of the crew cab. No problems with codes.
Good luck,
Craig

[UPST8NY]

Changed pump No Go

Any thoughts

Sucking air somewhere?

Maybe look at the tank selector switch?
Could I pull lines at this switch and dip them in a container of fuel to see if its pulling fuel from there?

Im about to throw a hammer at it or maybe my head

[skoalcowboy22]

WHERE ARE YOU IN NY? I AM BY ALBANY AND KNOW SOME WAYS TO FIX IT ILL PM YA

[UPST8NY]

Narrowsburg NY 12764 along the Pa border

[UPST8NY]

Well heres my sign!

I went out to the shop tonight and started to look at the lines .
I followed them back to the transfer switch and found I had crossed the flex lines at the frame .

The reason that it started and ran in the beginning is because I had filled both tanks before I had brought the truck in for the oil pan.

When I fired it for the first time it was off the front tank which I had not run out of yet.

The little use in and out of the shop was ok but when I went down the road I must have sucked the level down low enough that I couldnt pick up any more fuel.

Anyhow,what a difference that exhaust made .

[SMKSTAX]

Glad ya got it figured out. Nothing worse than a truck that sits, i know i just got mine started again with 2 new batteries. Today it goes in the shop for a new clutch so i can't wait to get her back.