Where do you connect the vacuum gauge on an EFI engine?

 

Uncap then use one of the unused ports on the vacuum tree located on top of the intake manifold (5.0/5.8L engines).

 

Doh! That should have been obvious if I'd stop to think about it.

Thanks.

 

Alright the truck has 18-19 inches of vacuum at idle and it holds steady while reving 3k with the truck just sitting. Didnt seem slow to return to normal. Also I unhooked the vac line to the regulator and the fuel pressure went up to 39psi. Got a new wix fuel filter today but its dark already.. Project for tomorrow I guess

 

I'm thinking of driving the truck with the vac gauge hooked up and see what happens when I have my reving issue. Think this would work?

 

I think thats what the fellow had in mind that you should do, take it for a drive with it hooked up and see what the vacuum gauge does.

 

Doesn't appear to me that you have a fuel pressure or vacuum issue, so I'll mention that the solution to a similar problem in another thread was to replace the MAP sensor. I have not read this whole thread either so I'll ask have you pulled the codes?

 

I think his fuel pressure readings are on the low side IMHO.

 

I should really learn to read better

 

I agree. I don't like these readings I'm getting. We'll see how much psi the fuel filter frees up. Not expecting a whole lot though..

 

I haven't yet. That's a good idea though.

 

Don't feel bad some days I'm lucky if I remember to read my own comments correctly.

 

They may be a touch low but that could be attributed to gauge tolerance or if the needle is bouncing just measurement error. In any event there is enough pressure there that it won't limit the engines ability to rev, that will only happen if cruising pressure is down in the low 20psi range and drops at WOT.

 

Well I was gonna pull the codes but I couldnt get the check engine light to come on. Pulled the gauge cluster and sure nuff somebody pulled the bulb out. I stole one of the others I knew worked but it still wont come on... Something interesting happened while I had it idling though. It dropped down to 500 rpm about died then reved back up to just under 1000rpm were it usually stays at. It only did that one other time so i ignored it. Could that be a symptom of a bad MAP? Anyways I still gotta do the fuel filter and run around with the vac gauge hooked up now

 

Alright driving the truck 3rd gear at 3000 rpm she is in the 15in range for vacuum. Then at the point where it wont rev anymore it would stay between 10-15 depending on how lead footed I was. And at WOT to the point it wouldnt rev anymore it dropped to zero..