I'm back in the IDI game!

[homelessduck]

Still trying to figure out the running rough issue. I played with some stuff today. Should the fuel pressure at the schrader be consistent or pulsing? It seems to drop pretty low between pulses.

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[IDIBRONCO]

With the starter cranking the engine over, you should probably see the pulses in pressure. The pressure goes up when the lift pump pumps and drops after that since there's a limited volume of fuel that comes out of the pump under pressure. If the engine is running, it should be steady since the pump is pumping faster. If you can maintain the volume, you'll also be able to maintain the pressure. See all of the threads on poor performance of Facett pumps if there's any doubts on that. You may not be able to get the engine running with the Schrader valve removed, but if you had the fuel pressure gauge installed, then the engine will be able to run.

 

[homelessduck]

With the starter cranking the engine over, you should probably see the pulses in pressure. The pressure goes up when the lift pump pumps and drops after that since there's a limited volume of fuel that comes out of the pump under pressure. If the engine is running, it should be steady since the pump is pumping faster. If you can maintain the volume, you'll also be able to maintain the pressure. See all of the threads on poor performance of Facett pumps if there's any doubts on that. You may not be able to get the engine running with the Schrader valve removed, but if you had the fuel pressure gauge installed, then the engine will be able to run.

I thought there was a check valve that helped keep the pressure more consistent? I totally forgot to check it while running haha. It started pouring and I was hurrying up to get everything put up.

 

[IDIBRONCO]

Let us know what it does while running.

 

[homelessduck]

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[IDIBRONCO]

There does seem to be an issue there. It may be time for a new lift pump. You could also try a different fuel pressure gauge. It looked like the needle on gauge still fluctuated at the exact same speed even as the engine RPMs rose. That doesn't seem quite right.

 

[homelessduck]

There does seem to be an issue there. It may be time for a new lift pump. You could also try a different fuel pressure gauge. It looked like the needle on gauge still fluctuated at the exact same speed even as the engine RPMs rose. That doesn't seem quite right.

Oh no it definitely bounces faster as the rpms go up. I'll pick up a new gauge the next time I'm in town though. I need a lower range one.

 

[IDIBRONCO]

If the pressure is actually fluctuating, that could very well be your running problem. If the pressure changes at that point, the pressure changes are most likely going into your IP as well. Can you imagine what that would do to your IP timing? I think I noticed that you have a Harbor Freight gauge. Maybe it's fine, maybe it's not. Instead of buying another one right off the bat, maybe you could try to find a mechanic shop that would be willing to hook their gauge up and check your fuel pressure. They should be pretty confident of the accuracy of their fuel pressure gauges.

 

[homelessduck]

If the pressure is actually fluctuating, that could very well be your running problem. If the pressure changes at that point, the pressure changes are most likely going into your IP as well. Can you imagine what that would do to your IP timing?

I'm pretty sure it is doing exactly that. When I timed it I had a hard time getting the timing accurate because the balancer mark was jumping around ( Tech Time with light ) . I planned on re-timing it once I got it to run better. That would definitely make sense. Erratic fuel pressure - erratic timing.

 

[homelessduck]

I think I noticed that you have a Harbor Freight gauge. Maybe it's fine, maybe it's not. Instead of buying another one right off the bat, maybe you could try to find a mechanic shop that would be willing to hook their gauge up and check your fuel pressure. They should be pretty confident of the accuracy of their fuel pressure gauges.

Ya it's a HF special. I've used it many times and never had a problem with it. But I do plan on picking up a quality gauge .

 

[homelessduck]

I hooked up an electric pump today to see how it would run. It wouldn't push fuel no matter what I did. So I unhooked it and it pumped fuel just fine off the truck. So I thought there must be a blockage somewhere.. So I pressurized the fuel inlet On the filter head to 10psi and it just held there... Doing this I also confirmed my HF gauge is actually pretty accurate lol. I must be missing something simple here..

 

[homelessduck]

Thinking out loud... The fuel goes in the filter head , through the filter and in to the nose of the IP. Excess fuel flows out the top of the IP and through the return lines.. A blockage in the return lines would cause leaks and possibly return hoses popping off.. It doesn't leak at all..The truck does run so the IP is getting fuel.. So the blockage must be at the top of the IP before it gets to the return lines..?? I tested it with power to the FSS by the way , which should allow fuel to flow through the IP and out the returns correct?

 

[Selahdoor]

Put clear lines on so you can see what it is doing.

 

[homelessduck]

Put clear lines on so you can see what it is doing.

I had clear lines on the supply side while I was sorting out the air intrusion issue. I haven't put one on the top of the pump return. I'll do that next. But nothing is getting passed the IP. It just holds pressure. I noticed with it running the clear line before lift pump looked like the fuel was back feeding as it pulsed.

 

[chillman88]

I tested it with power to the FSS by the way , which should allow fuel to flow through the IP and out the returns correct?

I've heard the IP won't bypass fuel unless it's turning (running) so it's possible that's normal. That's just what I've heard and perhaps Russ or Wes can confirm?