Airbound IP

[Shern]

About a year ago I set the drip timing on my pump (25degrees).
After I buttoned everything up, I had a hell of a time getting the car started. There was an obscene amount of cranking (over a 15-20 min period), pumping the pedal, and then eventually a horribly anemic start which sounded like only 1 or 2 cylinders were working. Another 20 seconds of pedal, we were back in business.

I set it again today (26 degrees), and now I cannot get the thing started. I've already run down my battery, got a jump and haven't made any progress with the cranking so I've relented for the night.

I cannot get enough air out of the IP by pumping the primer. It's creating movement from the spin filter to the pump -lots of bubbles and turbulence- but nothing is coming out of the return line. I'm parked on a slight incline so I believe I have an air bubble around where the #1 element is located.

Is there a way to clear air from the IP by hand?
I read a post where Stretch suggested removing the hard lines at the Injectors and then turning the crank in degrees until you found the start of delivery for each cylinder. Pump until it's leaking, then turn the crank and repeat for the next cylinder. My hunch however is that the springs in the delivery valves are too strong to be overcome by whatever pittance of PSI the hand pump creates.

What the hell do I do? How do I get air out of this thing?

[Diseasel300]

The primer handle only primes the fuel rack, it does not pump up into the hard lines (only rotating the engine does that). If you're not getting fuel through the return line, you likely have a defective primer handle. Its sole purpose is to push fuel through the fuel rack and out the overflow valve back to the tank. Cracking the hard lines and cranking until fuel squirts will greatly speed the priming process once you get the rack full.

[Shern]

Totally follow you, but there's no check valve for fuel going into the pump right? As far as I understand, it's only out.

I'm imagining a scenario where the air in the pump is preventing the pressure from building enough to overcome the relief valve.
Each primer pump is compressing that air slightly, which is bouncing the primed fuel back up the plastic line. Does this make sense?

This only seems to happen when I'm doing drip timing. I had both the plastic lines off the pump last weekend which means the pump should have been thoroughly drained of fuel. I primed it with no issues however. Why is this different?

[Diseasel300]

The lift pump has check valves in it to prevent the fuel from travelling backwards in the lines. If you have a clapped out check valve in the output of the fuel pump, you could get the air-spring scenario you state, but that's the only way. You do have the updated style primer handle right? The general consensus for years has been that the old-style needs to be 86'ed as the very first troubleshooting step.

[Shern]

I have the updated version.
I'm at a bit of a loss here... I'm going to walk over to auto zone and buy a battery charger.

Would loosening the OFV bolt while priming be of any use?

[Diseasel300]

You shouldn't have to loosen the OFV bolt to prime the pump, that's the entire purpose of the primer handle. Inability to prime with the pump handle suggests you have a blockage somewhere, bad delivery valve(s) in the lift pump, or a bad primer handle. Not much else in play.

[vwnate1]

I've had this issue too, with the newer blak top priming pumps I need to press and release at least THIRTY TIMES then I crank the engine a tiny bit to get the IP on a different cylinder, repeat until I feel back pressure when pumping and start it throttle mashed to the floor and I don't let off the throttle until all 4 / 5 cylinders are hitting .

The shop manual says the hand primer will pressurize one injector line, why I do it until I feel resistance then rotate the engine and repeat then start it up .

I probably miss read the manual but that's how I've been doing it every time I take the IP off or the fuel system apart and it works, every time .

[Shern]

Originally Posted by Diseasel300

You shouldn't have to loosen the OFV bolt to prime the pump, that's the entire purpose of the primer handle.

Totally. I was thinking perhaps the lift pump supplies far greater pressure than the primer. Enough to overcome the spring loaded OFV.

Originally Posted by vwnate1

I've had this issue too, with the newer blak top priming pumps I need to press and release at least THIRTY TIMES then I crank the engine a tiny bit to get the IP on a different cylinder, repeat until I feel back pressure when pumping and start it throttle mashed to the floor and I don't let off the throttle until all 4 / 5 cylinders are hitting .

The shop manual says the hand primer will pressurize one injector line, why I do it until I feel resistance then rotate the engine and repeat then start it up .

I probably miss read the manual but that's how I've been doing it every time I take the IP off or the fuel system apart and it works, every time .

This sounds familiar.

I'm not feeling any resistance on the primer -it's moving fuel as evidenced by the inlet to the pump, but not creating enough pressure to force air out. Perhaps rotating the engine is the right call. I assume you're doing this by hand? 90 degrees at a time or what?

[Diseasel300]

Originally Posted by Shern

I'm not feeling any resistance on the primer -it's moving fuel as evidenced by the inlet to the pump, but not creating enough pressure to force air out.

STOP.


If there's fuel moving at the inlet to the pump, it has to be going somewhere. It's either turning into pressure to force air out, or it's running through the pump and coming out the return line. This is simple physics, if the pump is drawing in fuel, it's displacing something else in the system.

[Diesel911]

Originally Posted by Shern

About a year ago I set the drip timing on my pump (25degrees).
After I buttoned everything up, I had a hell of a time getting the car started. There was an obscene amount of cranking (over a 15-20 min period), pumping the pedal, and then eventually a horribly anemic start which sounded like only 1 or 2 cylinders were working. Another 20 seconds of pedal, we were back in business.

I set it again today (26 degrees), and now I cannot get the thing started. I've already run down my battery, got a jump and haven't made any progress with the cranking so I've relented for the night.

I cannot get enough air out of the IP by pumping the primer. It's creating movement from the spin filter to the pump -lots of bubbles and turbulence- but nothing is coming out of the return line. I'm parked on a slight incline so I believe I have an air bubble around where the #1 element is located.

Is there a way to clear air from the IP by hand?
I read a post where Stretch suggested removing the hard lines at the Injectors and then turning the crank in degrees until you found the start of delivery for each cylinder. Pump until it's leaking, then turn the crank and repeat for the next cylinder. My hunch however is that the springs in the delivery valves are too strong to be overcome by whatever pittance of PSI the hand pump creates.

What the hell do I do? How do I get air out of this thing?

I have read what the other posted and perhaps will be repeating some of it in my own words.

The fuel supply system goes from the fuel tank through the Fuel Supply lift pump the spin on filter and into the Fuel Injection Pump housing and out past the Fuel Pressure Relief/Overflow Valve (that valve controls fuel supply pressure). You bleed the air out of the fuel supply system by pumping on the hand primer. In general when you have gotten the air out of that part of the system you will hear a buzzing or kind if slight squealing sound from the Fuel Pressure Relief/Overflow valve (and even when you hear that pump a bit more on the hand primer).

The Fuel Pressure Relief/Overflow Valves operates in about on the low end 8psi and on the high end around 18 psi.

Then there is the high pressure part of the fuel delivery system which is between the Fuel Injection Pump Elements and the Injectors. If air gets trapped between those the air has to compress to say as an example 1800 psi.
That means the fastest way to get the air out is to loosen the Fuel Injection Hard Line Nuts at the Injectors till you are always getting fuel out of all of them. Then tighten the nuts and attempt to start.

Even if your Fuel Supply Lift Pump was brand new if the vehicle has sat for a long time the fuel is going to seep back towards the Fuel Tank and that means a lots and lots of pumping on the hand primer as previously described to get the fuel primed again.

It is also possible for the Fuel Pressure Relief valve only to hold a lesser then the minimum pressure due to a weak spring. While that won't stop you from bleeding the Air out of the fuel supply system it means while you are cranking the Elements are not getting the optimal fuel pressure for them to fill properly.

If you have a fuel pressure relief/overflow valve that can be taken apart there is a ball bearing that is the valve and a spring. The spring can be stretched to a free length of 27mm and the valve reassembled and that usually raises the pressure.

[barry12345]

Quick answer may be to start the engine and run it with wd 40 sprayed down the throat with the air filter box open. Takes two people and it may then self prime.

You do have a problem existing though. Either the primer pump is bad . Or the pressure strokes are being bled off back through the lift pumps two check valves. The simple primer pump has no check valve itself. To clear the relief valve being open or far too weak. Just close off the return line from it. To see if you can build pressure.

All that is certain is that if you cannot build any pressure with the primer pump the reason should be located. I do not think it is the primer pump as it should also have been leaking fuel if it where. A substantial air leak before the primer pump is also possible or a pretty obstructed tank filter. Or tank accumulated Vacuum from an obstructed vent line. You want to remove the fuel tank cap and try pumping. As the easiest test first.

This overall basic fuel supply system is asking for attention. It perhaps had the same issue the last time you had a really hard time getting it bled.. More so that just getting the car to start. This issue as it worsens could create a problem on the road eventually. Easier and cheaper to deal with it now.

[Shern]

Thanks Diseasal/diesel911/Barry, all points taken.

Physics acknowledged, there is fuel moving out of the return hose. Potentially not enough to displace the air trapped likely from parking nose up.

One thing I’ve done differently this time, is performed this adjustment on a cold engine. Car has definitely sat for more than 12 hours without a start. Battery is on the charger now, will resume in the morning and report back.

Ps, Rebuilt the lift pump about a year ago with new valves, ofv spring stretch was checked two weeks ago and is at 27 mm. Fuel system tight, no leaks (finally).

[Diseasel300]

If fuel is coming out of the return hose, the rack is primed. Now it's down to getting the air out of the hard lines. Crack 1 and 2 and crank until there's fuel coming out. Tighten them back down and see if you can get it to start hitting on one or two cylinders. Once it starts hitting, keep cranking, it'll start.

[barry12345]

Just do not know and admit it. The system design is such that you should feel a really signifigant increase in the pressure. Required by using the primer pump. That is required to hear a normal relief valve open.

When and if it is not there is an issue of some sort. To get it to start I agree with the majority of suggestions. Members have presented. They also may get it to start. Yet a problem remains.

It is pretty easy to check it out step by step. It is a very simple system but can throw some nasty curves.

An example. The primer pump basically is creating a vacuum initially to draw fuel from the tank. The vacuum it pulls has limited abilities. Too much restriction say in the fuel tank filter or a tank vacuum buildup. Can partially technically defeat the lift pump. There are a few other senarios.

Could the situation create some power loss on an engine. I think it is possible. It could also be drawing a percentage of air in all the time as well. It sounded like you were advancing the injection pump to get a little more power than what you had.

This to me indicated you were not happy with what you had.

For example if you were seeing fuel flow out the relief valve but it was taking no noticeable more finger pressure to do. This from the initial start of pumping. The relief valve has an issue. Does not matter if you stretched the spring or not before.

If you are uncertain just close the output of the relief valve off. Then if the pumping becomes fairly hard you know at least one of your problems. In a good primary fuel supply system. You would actually hit a point where you cannot even force the plunger down. With that test. This test also tells you if the lift pump check valves are working properly. Or leaking back too much.

A pressure gauge is still your best overall friend to keep an eye on this primary supply system periodically. It is high on the list for potential road breakdowns. Plus performance issues.

[Shern]

Originally Posted by Diseasel300

If fuel is coming out of the return hose, the rack is primed. Now it's down to getting the air out of the hard lines. Crack 1 and 2 and crank until there's fuel coming out. Tighten them back down and see if you can get it to start hitting on one or two cylinders. Once it starts hitting, keep cranking, it'll start.

I've got fuel coming out of 2,3 and 4. One is still dry but it's beginning to hit.
Unfortunately I drained my battery again so it's back on the charger for now.
This is how it went down last time as well. Super anemic, aided by pumping the pedal until it fired up on its own.

Originally Posted by barry12345

Just do not know and admit it. The system design is such that you should feel a really signifigant increase in the pressure. Required by using the primer pump. That is required to hear a normal relief valve open.s

This to me indicated you were not happy with what you had.

.

Come on, now... half the stuff I do to this poor car is completely unnecessary.
It's how I learn! I'm curious to see how it runs at 26. If it's no good, I know where to find 25 again.

I did your test re: pinching off the return line, and yes, it gets to the point where pumping is extremely difficult. HOWEVER, this gave me an idea.

I pinched off the return and pumped until it got pretty firm. While continuing to prime, I let the clamps off and each time a few large bubbles came shooting out of the return. I did this four or five times. All this time, I was seeing air in the pump supply hose. Now there is absolutely zero air in the low pressure side.

Whether this worked or not, well, we'll find out when the battery's charged.