Fuel pressure problems

[nullset]

Hi all,

I'm still working on getting 2930 running again. It runs on ether, but does not run without it.

I've checked the fuel pressure from the pump ( going straight to a pressure gauge ) and it reads roughly 90psi. This leads me to think the problem isn't in the pump.

When I hook up the KJet CIS tester, I see lower pressure than that - I think it was around 50 psi, no matter whether the valve on the tester was opened or closed.

I've replaced the PPR Oring and it didn't seem to make a difference.

I've got a few days to plan before going back up to work on it again.

Does this sound like a mixture unit that needs to be cleaned or rebuilt? What sets the pressure?

Anyone that is willing to spend some time in Buford, Ga this weekend is welcome to help out!

[sdg3205]

Have you verified your injectors are all functioning? Spray test? Did you set a baseline with the injectors in glass bottles? Is your cold start valve operational?

[nullset]

Have you verified your injectors are all functioning? Spray test? Did you set a baseline with the injectors in glass bottles? Is your cold start valve operational?

I've verified that the injectors are functional, but they do not spray when the pressure plate is pushed down - at least not reliably. During this test, the RPM relay is bypassed ( fuel pump is running).

I believe the cold start valve is working but am not 100% certain of that. I haven't tried pulling it.

[sdg3205]

At 50 psi those injectors should be spraying when the plate is pressed.

Assuming the tank is clean, the fuel filter isn't clogged and you've got fuel to the distributor, my guess is it's a plunger issue. You can try to remove the send line at the distributor and drop it in a jerry can to ensure you are in fact getting fuel to the dist. That's how I empty my tank in the fall. If for some reason you're not, then you know the problem is upstream.

Are you 100 percent sure the fuel pump hoses are correctly installed and NOT backwards?

[escobar30301]

Replase the fuel accumulator u gas pressure going back to the gas tank if the part is defective


Sent from my iPhone using Tapatalk

[Bitsyncmaster]

Have you changed the fuel filter? I have seen one fuel filter on a D cause zero pressure at the FD. I would also guess a ruptured fuel accumulator could also reduce pressure at the FD.

[DMCVegas]

Ok now, let's get back to basics.

What work have you performed thus far on the fuel system. Let's start from there first.

[nullset]

I bought the car 5 years ago. I replaced the pump, filter, accumulator, and injectors at that time.

I haven't had time to mess with it lately and let it sit for too long, which is how we got to where we are today. I've flushed the fuel lines by disconnecting the feed and running the pump until fresh clean gas comes out ( after having pumped out the tank and filled it with fresh gas ).

I have verified that the pump is making fuel pressure. I've pulled the injectors to look at the spray pattern, but they did not spray when the plate was pushed down. Sometimes I get a small amount of spray, but it's not consistent.

They do not appear to be dirty from the outside.

I've also replaced the PPR oring per other suggestions.

With a properly working KJET system, what pressure should I see when the pump is running but the engine is off, and where should I see that pressure? If it's low, what should I start with for diagnosis?

Thanks for all your help so far.

[Jonathan]

I think someone else was hinting at it being a possible problem with the return line back to the tank.

If the pressure is to be regulated properly, and this would apply to any fluid system, it needs there to be flow through the system. Otherwise, if things can't move, the pressure you see would be equivalent to a dead-head pressure, i.e. the isolation valve on the discharge of the pump is closed.

Perhaps there is some reason the fuel return line isn't working as intended? Plugged or capped off maybe? The return connection off the side of the distributor is the larger diameter one with the double connection, the second connection being from the backside of the frequency valve.

[nullset]

I think someone else was hinting at it being a possible problem with the return line back to the tank.

If the pressure is to be regulated properly, and this would apply to any fluid system, it needs there to be flow through the system. Otherwise, if things can't move, the pressure you see would be equivalent to a dead-head pressure, i.e. the isolation valve on the discharge of the pump is closed.

Perhaps there is some reason the fuel return line isn't working as intended? Plugged or capped off maybe? The return connection off the side of the distributor is the larger diameter one with the double connection, the second connection being from the backside of the frequency valve.

As far as I can tell, there's no blockage on the return path. There was a possible kink in one of the lines attached to the accumulator but that has been resolved. I'll check the pressure as it bleeds off when I'm back to be sure.

[David T]

As far as I can tell, there's no blockage on the return path. There was a possible kink in one of the lines attached to the accumulator but that has been resolved. I'll check the pressure as it bleeds off when I'm back to be sure.

Confirm that when you replaced the fuel pump you hooked the output of the fuel pump to the feed line, NOT the return line. If you still aren't spraying at the injectors you either have a bad F/D or bad injectors (or possibly both!).

[nullset]

Confirm that when you replaced the fuel pump you hooked the output of the fuel pump to the feed line, NOT the return line. If you still aren't spraying at the injectors you either have a bad F/D or bad injectors (or possibly both!).

The car has run since the last time the fuel lines were removed from the pump. I am confident that they are correct but I'll check again - it never hurts.

[DMCVegas]

I bought the car 5 years ago. I replaced the pump, filter, accumulator, and injectors at that time.

I haven't had time to mess with it lately and let it sit for too long, which is how we got to where we are today. I've flushed the fuel lines by disconnecting the feed and running the pump until fresh clean gas comes out ( after having pumped out the tank and filled it with fresh gas ).

I have verified that the pump is making fuel pressure. I've pulled the injectors to look at the spray pattern, but they did not spray when the plate was pushed down. Sometimes I get a small amount of spray, but it's not consistent.

They do not appear to be dirty from the outside.

I've also replaced the PPR oring per other suggestions.

With a properly working KJET system, what pressure should I see when the pump is running but the engine is off, and where should I see that pressure? If it's low, what should I start with for diagnosis?

Thanks for all your help so far.

I don't have my Workshop Manuals with me, so I couldn't tell you the operating and rest pressures. Instead check your Workshop Manual to verify those numbers. But what you're going to want to do is first connect up a fuel pressure gauge and follow the instructions to test your Cold Pressure, Warm Pressure, and your Rest Pressure Bleed-down. That will start to give you some good ideas as to the functionality state of your Warm-Up Regulator, your Primary Pressure Regulator, and finally your Accumulator. Do that and then let's see where you're at.

First thing is that we want to ensure that properly pressurized fuel is getting to the Distributor. Then we can focus on the internal functionality next, and then work our way down the hoses to the injectors next.

[sdg3205]

The car has run since the last time the fuel lines were removed from the pump. I am confident that they are correct but I'll check again - it never hurts.

I've heard reports that a car will run to some degree (like crap) with the fuel lines routed backward at the pump. Of course, I've never tested this so I can't confirm anything, but it's something to bare in mind.