97 454 L29 Long Crank

[someotherguy]

According to Rock, which isn't always 100% correct, but they're usually pretty good - but like he said, it can be tricky, especially when the specs don't use the same terminology. The part # you listed, AC Delco 2173073 has specs that say "max pressure reading 36 psi" - whereas some of the other offerings such as the Standard PR217 says "operating pressure 57 psi"

So, do you have the incorrect FPR? I really can't tell, but that 36 psi in the specs is a red flag, to me.

Richard

 

[Spareparts]

I bought 4 or 5 different FPR before i finally got the one i needed and sorry to say i can not remember exactly what one i installed but i will try to get a mirror and see if i can find a number on it.
I think PR217 did not have the proper pressure that is lists.
Here is another option that i would bet works. Says it is adjustable from 30 to 100PSI

DeatschWerks 6-M02-4 DeatschWerks Fuel Pressure Regulators | Summit Racing

Free Shipping - DeatschWerks Fuel Pressure Regulators with qualifying orders of $109. Shop Fuel Pressure Regulators at Summit Racing.

www.summitracing.com

 

[TN454K3500]

So here are the results... scratching my head a little.

I went back to the manual as @Schurkey suggested and followed the steps for testing the fuel system.

The first thing I noticed it said to do different than I had done was monitor the fuel pressure with the fuel pump on. I had just had the gauge laying on the intake and looking at it after the fuel pump cycled off... Rookie mistake...

It won't let me upload the video, but it does this:
Key on, Pump On (~2 seconds), 58PSI, which is within range
Pump Cuts off, drops immediately to 50-52 PSI, then starts dropping like I had described before....

In the manual it says to pinch off the return line like you all have suggested and I slowly did so, never really seeing any different result until I pinched it so hard it hit 100PSI...

With this result, the manual says, "Inspect the fuel feed line between the pinch and the throttle body." Which I am assuming this is generic for older models but that would include the injector and FPR for my engine, but if the hose is pinched then the only leak path is through the injectors, at least that's the way it works out in my head. Unless there was an external leak and as much as I had messed with this there would be a puddle in the floor if there was....

On another note, on one of the manual steps (outside of the flow I was following) it says to start the engine and open the throttle quickly while watching the fuel pressure. When I do this it does hit the 57-60PSI which is why I am assuming I don't see negative performance... or at least negative enough to be noticeable.

I feel like I am back at square one... I need to drive it to see if the long crank still exist with the different pump. I wish I had done this same test with the other pump installed. If it is, then I am back to where I was when I changed the injectors originally thinking they were leaking some.

 

[Mangonesailor]

but if the hose is pinched then the only leak path is through the injectors

You need to pinch both the supply and return line to 100% rule out the fuel pump check valve leaking pressure back to the tank. But you could still have a stuck injector

 

[someotherguy]

Wow.. I'm surprised that pump can deliver the running pressure readings you're getting. I guess I take it back when I said you have the wrong one.. apparently they'll just take a pump and stick it in a box and if it fits a particular range of pressure it's OK as long as you have the correct regulator in there.

Standard PR217 is what I used in my '96 7.4, for what it's worth. Along with the Bosch yellow 4 hole injectors. No more long crank/stumble/smoke to idle when warm.

Takes squinting just right but you can read the PR217 on the box .

You must be registered for see images attach

Richard

 

[TN454K3500]

You need to pinch both the supply and return line to 100% rule out the fuel pump check valve leaking pressure back to the tank. But you could still have a stuck injector

10-4, did not think about that. I’ll give it another try. I’m gonna have to get someone to help me. I want to try to leave any clamp completely off and then turn the key on, let the pump prime and when it shuts off then put clamps on to completely block it to see what happens.

@someotherguy I was too, I expected something in the 80s. It pegged the gauge. I know there is risk to damage FPR but I had to know. Didn’t leave it in that condition but a second.

Thanks for the sharing actual one you are using. That is one of the few that calls out operating pressure within specified range. Those are the same injectors I installed as well.

For the AC Delco I installed it just makes me wonder if the “maximum reading pressure” of 36 PSI is what it will hold in key off position and that is the bleed down. In my head it’s just hard to grasp a new set of injectors leaking/sticking.

I’m gonna be out of town for a little over a week so I won’t be able to wrench. I’m gonna order that same FPR and get it in. I’ll report back when I do.

Thanks for all the advice and discussion. Y’all have a good 4th!

Ross

 

[Eurocopter]

My truck fires up good when cold, but when it's hot it can have a long crank after sitting. If you turn the truck off then turn the truck back on (within ~10 mins) it fires up immediately, just like when it's cold. If it sits for ~30 mins, then it has a long crank. If you barely give it some gas while starting it then it will fire right up like it should.

I have recently replaced tank fuel pump, transfer fuel pump, injectors (precision auto injectors), FPR, FPR vacuum hose, distributor, distributor cap/rotor, plugs and wires. Part of it was to try to mitigate this issue and part was due to other reasons. It did this BEFORE and AFTER these changes, basically no change to this particular issue.

I am going to do some testing with the fuel pressure to see If I loosing fuel pressure in the rail somehow, but it just doesn't make sense how it starts up so good when it's cold.

Just throwing it out there to see if someone has had this issue before or if there is some vacuum lines or something that could cause this....

Thanks

Lawrence Tolman. Youtube. "Vortec Big Block 7.4 Injectors and Regulator: curing a hard start

 

[gwolf]

On this motor this condition is always injectors. Everytime. BTW if you buy the AC Delco injectors from Rock Auto they come with the new clips. And they are new 3 hole injectors.

 

[454cid]

On this motor this condition is always injectors. Everytime. BTW if you buy the AC Delco injectors from Rock Auto they come with the new clips. And they are new 3 hole injectors.

It can also be a bad fuel pump. I was amazed when a new fuel pump "fixed my injectors" and the truck didn't start hard anymore.