How about running a wire from the IVR to the post we think it is and grounding the other post to see if it pegs?

Thanks
mjac

 

I wanted to ask you a question before I put it out in the general forum. I have a low vacuum reading, 10-12, that is steady, not pulsing. I checked the engine a month of Sundays for an external leak, first checked the brake booster, nothing, checked the whole engine with the gas from a propane torch, nothing, shot every seam with carburetor cleaner and found a very small vacuum leak on the front of the manifold on the passenger side, the rpms ticked up just a little bit. Went back to the same spot and poured on propane gas, nothing. I was going to do a compression test and then adjust the valves (it is due). Can bad valve timing cause this low vacuum reading, the truck is running pretty bad, especially down low? If that is not it, I have an internal vacuum leak? How can I verify that before pulling off the manifold? That is the main question.

Thanks
mjac

 

That sure sounds like low ignition timing or incorrect dwell if an old one with points
Pull the PCV valve from the valve cover and see how much vacuum is on the other cover with it removed versus putting it back in there
I am trying to visualize your what? 72 Econoline? what engine?

 

83 Ford E250 with a 302, Edelbrock Dual Plane Manifold, Edelbrock 500 cfm Performer Carburetor(Standard not RPM), Ford Street/Strip DUI Distributor from Performance Distributors.Denso Iridium Plugs,

I am a little loss, pull the PVC Valve then check the vacuum at the filler cap on the other valve cover?…And what exactly will this show?
I did check the vacuum at the PCV Valve and it was the same low 10-12 lbs. I did read somewhere about pulling one of the plugs in the manifold and check the vacuum there, I do not know what this is supposed to show though.

Thanks
mjac

 

That is the test to show if the PCV system is working
On an engine that is working properly, you leave the PCV in there and pull the vent on the other valve cover
Place a small piece of paper over the vent hole and the PCV valve should have enough vacuum in there to suck the piece of paper down to contact the grommet
You pull that small piece of paper away and the vacuum in the crankcase wants to suck the paper back down to the grommet
That is normal
With an intake leak into the valley (crankcase) the vacuum will be less or gone at idle and may increase with engine speed
That problem used to be common on 2.9l engines in Rangers and Bronco IIs
Sucked part of the intake gasket out in the valley
Pretty hard to diagnose really
A smoke test will shoot smoke out the valve cover breather

 

If I understand you correctly, if this test shows low crankcase pressure, there is a pretty good possibility there is an internal vacuum leak like an intake manifold gasket leak around one of the ports?

When I did the smoke test with a rigged up smoke machine using a little dc tire inflator and a smoke pot, I taped over the breather hole and put the smoke through the PCV Valve Grommet. Wasn’t sure it was working being rigged up and all but smoke was pouring out of the dipstick, so I guess it was.

The plan is to do a static compression test, a running compression test would not give me much more information except what valve in the cylinder was acting up, and then adjust the valves using a technique I read about. The way this guy did it, he would take one cylinder at a time, bump the engine until the exhaust valve was all the way open which meant the intake valve was closed, adjust the intake valve by torquing down until there is not up and down movement of the push rod and give it (I believe) another 3/4 turn. Then do the exhaust valve in reverse. I am not sure how I will tell the exhaust valve or intake valve is all the way open but I guess it may be apparent, I don’t know. He said this improved performance even in an engine that had been “tuned.” One guy said his engine was running very poorly and two cylinders had no compression (I think he said he had low vacuum too) and after he adjusted the valves all of the problems disappeared.

Edit: Got the Alternator today, going to put it in and see if the draw disappears and it was a diode like y’all said.

Thanks
mjac

 

During the smoke test, you want that smoke in the intake manifold looking for it to come out the valve cover if concerned about the intake leaking internally
There is no real good failproof way to test for that IMO
That is why I referenced the PCV test to check for subtle differences in idle quality and vacuum numbers while observing the piece of paper
I agree with checking the valves, a fluctuating gauge you do not have you said right?
What is the ignition timing set at?

 

To do the smoke test right, you introduce the smoke into the manifold? Does that mean taking out one of the plug bolts in the manifold, putting a fitting in there and introducing the smoke into that fitting? Is there a particular bolt plug that should be taken out? When you say “ looking for it to come out of the valve cover,” where, the breather, the PCV Valve, the PCV grommet?

it would seem you figure it is an internal vacuum leak by process of elimination. You eliminate everything else and that is the only thing left, then you are pulling manifolds.

The vacuum gauge when hooked up in various places, is a steady low vacuum reading about 10-12, it is not pulsating or wildly bouncing. From what I understand a wildly bouncing vacuum reading means a stuck valve or a valve that is not seating and a steady low reading means a vacuum leak. Do you approve of that valve adjustment technique and is it difficult to determine when the exhaust or intake valve is fully open when looking at them?

The ignition timing set with the DUI Performance Distributor is backyard, advance to the highest vacuum reading. ( When the vacuum numbers were correct) I don’t know the exact degree, that is something I have been meaning to do with the timing light I bought.

Thanks
mjac

 

This is just Monday and Tuesday to you, this is Marci Gras in New Orleans.

 

I wish you were still posting, finding out what the parasitic draw was was hilarious.

Thanks
mjac

 

Borrow a timing light from Autozone or another parts house to set the timing
Motorcraft spark plugs next time

 

I gotch me a timing light, an Innova 3555, I just haven’t used it.

What’s wrong with my Densos?

 

it's about impossible to get one set correctly with a vacuum gauge
Set it with a light to a number, then you can adjust up or down if it pings or lacks power
I used to run my Z-28 at 20 degrees here at 5000 feet
You can adjust the timing to the highest vacuum the motor will achieve and then back it off a bit
That will be close but still not a number
You need a few numbers to verify timing is correct and at the right time
Like checking it with the vacuum advance off and testing how much and when the mechanical advance kicks it
You can also play with spark port versus manifold vacuum for the vacuum advance supply
You might be able to get it to run decent at your altitude and fuel quality
Those Densos will leave some fuel behind on a Ford
I have done a ton or emissions testing over the years
Denso in a Nissan, Honda or Toyota, Motorcraft in your Ford

 

To tell you the truth, after investing in a $400 DUI Performance Distributor, $40 in Denso Plugs and a new set of wires (The brand escapes me right now) I was not impressed with the spark it produced compared to the the old, worn out ignition system. I was expecting lightening bolts. Performance Distributor recommended using manifold vacuum to smooth out the idle. But I can’t do anything until I straighten out this low vacuum. They say in the vacuum gauge manual a low, steady vacuum reading can be caused by bad valve timing, I am hoping that is what it is. You never said whether you go for this guy’s valve adjustment technique.

mjac

 

Those old original Duraspark systems sure would throw lightning (I run a Duraspark on my 69 Boss 302) (40kv. is enough)
If you can see lightning, the plug wires need to be replaced and the cap and rotor checked
Those fancy valve adjustment techniques do work and I use that procedure on my Boss 302 with a radical camshaft
Adjust the intake when the exhaust starts to open
Adjust the exhaust when the intake starts to close
Thet call that the EO-IC method and is about the only way to get one correct with a radical cam profile
You can just torque yours down to the spec as they are positive stop rockers (no adjustment) (unless you swapped heads or the motor with earlier)?