Tank to pump hose routing

[chaseincats]

Hi gang,

Could someone take a picture of how the hose that connects the tank to the fuel pump is routed on a 77/78?  Mine has always sort of hung under the car suspended over the half-shafts with various zip ties which isn't right.

[Yarb]

There is a hole in the frame where the hose is routed. Don’t have a pic at the moment but it’s easy to see.

[Captain Obvious]

Here's a pic I hoovered from the web some time ago. Not my car:

[chaseincats]

4 hours ago, Captain Obvious said:

Here's a pic I hoovered from the web some time ago. Not my car:

Thanks! This is interesting and I'll tell you why.  The car ran horribly after I replaced the old tank-to-pump hose (due to age) and I eventually found that I had 20psi coming out of the fuel pump due to me zip tying the tank-to-pump hose higher than where it had been before being changed.  After lowering the hose (to a couple inches over the half shaft where it had been i believe) I saw my psi go up to 32.

The car used to run great before I replaced the hose so I must not be hanging it right as it idled at 36psi.  Long story short, I don't understand how these pumps are able to spit out 36psi when routed that high compared to how I had it.

Edited Sunday at 06:43 AM by chaseincats

[Captain Obvious]

The fuel pressure on the outlet side of the pump should not be affected by the routing of that hose. Assuming, of course, you didn't kink anything.

I wonder if maybe you've got air in that line which somehow can't get purged out because of the routing. Not sure if that's a thing, but maybe something to think about and look into?

[Yarb]

You mentioned pump and damper replacements. What did you install. Factory pumps are available very expensive. Dampner nla.

[chaseincats]

1 hour ago, Yarb said:

You mentioned pump and damper replacements. What did you install. Factory pumps are available very expensive. Dampner nla.

Nah, the only things I replaced were my 20 year old hoses

[chaseincats]

Ok so here's some more information from tonight's festivities:

 - I think the original issue wasn't the height of the hose, it was that I had it zip tied too tight (kinked like @Captain Obvious suspected).  I turned the car on and had someone watch the fuel pressure gauge in the engine while I wiggled the hoses from all angles/pulled it as high up under the car as I could, and it didn't change - which is why I think it was kinked

- With the car turned on we're still sitting at ~30 psi at idle with the vacuum hose connected to the fpr and 38psi with it unplugged, idling, with my finger over the hose to prevent the vacuum leak.

I just took the car around the block and it is incredibly sluggish (acceleration sits in the 15-17 range on the air fuel ratio gauge).  I pulled over and unplugged the fpr vacuum hose and with 38 psi, the car is a rocket again - so the gauge fuel pressure gauge is right there definitely is a fuel pressure issue here...

[Captain Obvious]

Hmmm... 38psi with the vacuum line pulled off the FPR sounds good. And 30 psi with that line connected is OK too.

Are you able to see the fuel pressure gauge WHILE you are driving? I'm curious to see if the 38 drops significantly when there is more than just a "light idle" load on the engine. In other words... Your fuel system may be able to deliver enough fuel AT IDLE and still maintain 38 psi, but the trick is that it takes a really small amount of fuel to maintain idle. I'm thinking that maybe the system can idle fine at 38, but as soon as the fuel delivery requirements get higher (like when you are driving around), the system doesn't have enough compliance to maintain proper pressure under higher demand conditions.

And that's a typical symptom of a restriction somewhere. Fuel filter, clogged check valve, something like that.

 

 

[chaseincats]

13 hours ago, Captain Obvious said:

Hmmm... 38psi with the vacuum line pulled off the FPR sounds good. And 30 psi with that line connected is OK too.

Are you able to see the fuel pressure gauge WHILE you are driving? I'm curious to see if the 38 drops significantly when there is more than just a "light idle" load on the engine. In other words... Your fuel system may be able to deliver enough fuel AT IDLE and still maintain 38 psi, but the trick is that it takes a really small amount of fuel to maintain idle. I'm thinking that maybe the system can idle fine at 38, but as soon as the fuel delivery requirements get higher (like when you are driving around), the system doesn't have enough compliance to maintain proper pressure under higher demand conditions.

And that's a typical symptom of a restriction somewhere. Fuel filter, clogged check valve, something like that.

 

 

Just to be sure I'm not barking up the wrong tree with blockages/restrictions - the pump wouldn't be the issue right?  Since it's an electric pump it will either work or it won't and not become weaker, correct?  The pump is probably a year old

[Yarb]

What pump are you using? Factory or aftermarket?

[chaseincats]

30 minutes ago, Yarb said:

What pump are you using? Factory or aftermarket?

Aftermarket - this one