ZZ Ramjet fuel press. reg. issues

[peter]

When I did my swap last year, I also checked my fuel pressure to be sure it met the minimum requirements as stipulated by GM for a Ramjet engine. The Ramjet manual states that the system needs between 42-55 psi, but then later on it states that GM Vortec-equipped vehicles are perfect for these engines due to their fuel pump capacities. The pump pressure of a Vortec engine is to be between 55-62 psi. Huh?
In any case, last year I had approx. 43 psi at the rails at idle with the vacuum line off. Now, after replacing my fuel pump (due to this issue and mostly due to an erratic fuel gauge issue) and fuel filter, I've got 46 psi with the vacuum line disconnected, and 40 with it connected. Far as I'm concerned, still way lower than what the pump can supply. The only possible explanation is that I got a defective Ramjet fuel pressure regulator from the get-go. With the vacuum line at the regulator disconnected, the pump should allow me to see at least 52 psi.
So I tried something else. I've driven the truck around all this week with the regulator unplugged, therefore supplying the engine with the maximum possible fuel at all times, even at idle. In theory and with a fuel pressure up in the 50-60's, I should have experienced flooding or excessively rich conditions, shouldn't I? Nothing! If anything, the engine "seems" to experience less pinging when running at higher temps, but not by much. This whole fuel pressure issue was brought on by the pinging issues which I didn't have last year. When the engine is running at around 200-220* and ingesting traffic-type underhood air temps, she detonates at load. I didn't have this issue last year. When they rebuilt the engine, they shaved the heads 10 thou, I'm sure that this may have something to do with it. These engines come tweaked out of the crate. I imagine that even just 10 thou would be enuf to cause other deficiencies like lower fuel pressures to show up. At least I'm hoping so.
I picked up a fuel pressure regulator from GM yesterday, will try to replace it today. If it doesn't make a difference, then I guess I'll have to rely on the 110 octane race gas I bought to help me see the 13 second bracket I'm gunning for. Anyone see something I'm missing?

I'll keep y'all posted

[SafariRob]

I certainly don't see anything you might be missing concerning your van's detonation problem, Peter.
Since I've added the MSD timing control to my 305 equipped van, I've really become aware of how engine temperature affects detonation. It doesn't take much of a temp increase, either. My van will run fine until the temperature gauge reads 200F (where is usually runs with the 195 thermostat), then the detonation starts when shifting into 4th. Cranking back the timing just 3 degrees brings silence again.
Some time ago, Popular Hotrodding magazine ran an article on controlling detonation. I don't remember all the points they covered, but high on the list was controlling engine heat; both the coolant temperature and the intake air. In particular, they recommended ducting in outside air for the engine to breathe. I'm kicking around ways to do that on my V8ized Astro, but there isn't much room under the hood, as we all know.
One thing that was suggested surprised me; they recommended filing the sharp edges off the sparkplug ground electrodes, making them look like a U instead of the squared off end they come from the manufacturer with.

[Mr_Roboto]

The vacuum line on the regulator doesn't reduce the overall FP peter, it reduces it at idle. It should drop something ~3-5 PSI at idle, the reason for this is that the idle is improved because the amount of fuel a pulse width to the injectors can deliver is reduced. With the line off the FP should go back pretty close to the baes (vacuum line off) pressure. If your FP is capable of supplying the fuel pressure and your return line is big enough, having the Vortecs run a HIGHER pressure is a non-issue. I'm using a Tuned port pump capable of delivering 60 PSI with my 4.3L TBI at 13 PSI with no problems. Idle FP isn't exactly the greatest indicator of pump health. You really need to check and see if you're dropping pressure at wide open throttle.
If you don't think the stock tune is getting the job done find someone with a wide band or blow the $$ at a dyno, quite frankly I think that's what you need to do especially since that's now a non-stock engine, .030 makes a good bit of difference if the computer doesn't have much allocation for modification of the tune. I wish we would have had time to hook mine up at the campout, it would have probably explained a lot.

[e7ats]

I still think your Fuel lines are too small to handle that kind of volume of fuel. Even with a high flow pump you have to have lines big enough to handle the volume.

[peter]

SON OF A FREAKIN' B .............

Replaced the regulator yesterday. While doing so, I discovered an adjuster set screw on the head of the regulator. It's a Torx screw with a pin in the center which prevents a standard Torx screwdriver from turning the screw. Seeing as I had the new regulator anyways (special order = non-returnable), and seeing as I had to remove the old regulator to get to the set screw, I up'n replaced the item after breaking off the pin in the set screw.
Before touching the adjuster, I was now up to 52 psi at idle with the vac. line connected. Keep in mind that nowhere in the Ramjet manual does it state that I'm to check pressures with the vacuum line disconnected. Disconnected I was pretty well where Robo figured, around 56 psi. This was all I woulda had to do from the get-go. In other words, GM had the regulator set up to deliver 40 psi at idle where it should have been closer to the minimum 43 psi as specified in the Ramjet instructions. Anyways, after tinkering with it for awhile, I set it to 53 psi with vacuum and then took it for a spin. It seems like the engine doesn't want to detonate as much, if at all. It's hard to tell, seeing as I was running in 4wd (it was raining) and the outdoor temps were only in the 60's. But even after allowing the engine to get to the hotter end of the temp scale, she didn't seem to wwanna ping or detonate. She feels peppier as well, and starts better also. I think that this issue has been resolved for the most part.

It's a pisser though, this fuel pressure issue woulda been so simple to fix if GM had mentioned that the regulator was adjustable. So far, it's cost me;

- $450 for a new pump (though the fuel sender operation was erratic, so kinda justifiable just the same)

- $350 for the replacement of a section of fuel line and filter by GM (which I ain't paying, they're gonna waive it in trade for me taking out the engine under warranty)

- $150 for a new fuel tank (I wouldn't have noticed that it was starting to rust out up top if I didn't change the pump...)

-$120 for a new regulator which I didn't need


Am I done now, Oh Great AS Supervisor in the sky? Can I just worry about mundane stuff like a paint job, washing and vacuuming and mebbe an oil change and grease, huh? Ya think, maybe?

[peter]

I still think your Fuel lines are too small to handle that kind of volume of fuel. Even with a high flow pump you have to have lines big enough to handle the volume.

Paul, the Ramjet manual states that any vehicle equipped with a Vortec engine has the necessary pump and proper line sizes. As well, my issues were always at part throttle, never at WOT. I appreciate the advice, though what I'd really like is a cash donation....

[Mr_Roboto]

Hey petey, you mentioned something about race gas. Did you put any in your tank, and did it help with the detonation?

[peter]

Haven't tried it yet. I'm sure it'd fix the detonation I had/mebbe have, but that's not a practical solution. Can't see myself driving to florida with 20 gallons of 110 octane which I'd use to spike a premium pump's contents with LOL.