New to me 1990 Shelby Daytona VNT

[kuzman83]

As far as I could see on the vac diagrams I've looked at the only two I removed were the check valves for the purge canister and the green oriface on one of the vnt solenoids. The check valves and lines for the cruise control all looked like they were in decent shape so I left those alone.

Once I'm done with these lines I have a K&N drop in filter to put in, new fuel filter, spark plugs, wires cap and rotor that need to go on. I did check the timing and it was retarded 10 degrees or so. Makes me thing the dist. is off at least one tooth. After the motor work is done I'll be tackling the headliner and interior issues.

[kuzman83]

I went to finish up installing my new vac lines and found one of the nipples broken off on the #1 VNT solenoid. At a stand still until I can find another one. Off to the classifieds....

[Reaper1]

I think it might be a pretty common solenoid. Check out how it works by hot wiring it and blowing through the nipple (wow, that sounds so wrong). Then check the others. What you might find is that you can get it at the junkyard for a few bucks.

[kuzman83]

Well I managed to find one from a guy that is parting out a VNT car so that is all taken care of. I still have a couple issues though, looking for some insight. When I first start the car it runs great, throttle response is fine, revs up no problem. Then after about 2-3 mins of running, I hear a very noticeable humming sound from the rear of the car (fuel pump). As soon as the humming sound starts, the car starts misfiring, no throttle response, runs like crap. The humming noise will get gradually higher pitched and then eventually stop, as soon as the noise stops, the car smooths out and runs great again. Here is the list of items I've replaced:

Fuel filter (both in tank and in line)
Fuel pressure regulator
All the vac lines
ASD relay

I have a spare Walbro laying around I am going to install today to see if that fixes it. The humming noise is directly related to a drop in fuel pressure. As soon as the noise starts the pressure drops. The only thing other than the pump itself I can think would cause this would be the computer. Any other suggestions?

[ShelGame]

The computer doesn't control the fuel pump except to turn it on via the ASD.

I the computer was cycling the ASD, it would also affect the coil and injectors, which are also powered thru the ASD.

I think the pumps have an internal pressure relief valve. Maybe that is sticky or leaking? Maybe the sock is clogged or pinched?

[2.216VTurbo]

Some of the pumps don't have that little ridge/nipple on the outlet from the pump. I had a similar issue, sometimes OK then after warm up total Crap! The hose was pushing off of the pump outlet partially when everything warmed up. Strangely enough, it was also a Daytona...

[kuzman83]

Well I installed the Walbro and the problem is gone. Runs great now so on to the next problem. The turbo is overboosting like crazy. I checked all my vac lines at least a dozen times and everything looks to be hooked up correctly, including the green oriface. The only vac related change I made was the diameter of the line that goes from VNT solenoid #1 to the top nipple on the vnt controller on the turbo. It is 3/16" instead of the 1/4" line it was from the factory. Would this make a difference? Other than that I need to start going through my fsm and powertrain diagnostics books and start trouble shooting. I am not sure how to check the vanes on the turbo for movement other than maybe taking it off. I do have an extra solenoid pack with vnt #2 and 3 I might try swapping out and see if that makes a difference.

[5DIGITS]

Well I installed the Walbro and the problem is gone. Runs great now so on to the next problem. The turbo is overboosting like crazy. I checked all my vac lines at least a dozen times and everything looks to be hooked up correctly, including the green oriface. The only vac related change I made was the diameter of the line that goes from VNT solenoid #1 to the top nipple on the vnt controller on the turbo. It is 3/16" instead of the 1/4" line it was from the factory. Would this make a difference? Other than that I need to start going through my fsm and powertrain diagnostics books and start trouble shooting. I am not sure how to check the vanes on the turbo for movement other than maybe taking it off. I do have an extra solenoid pack with vnt #2 and 3 I might try swapping out and see if that makes a difference.

Does this vehicle have the catalyst removed, a low restriction muffler or both??

I'd suggest staying with the factory line sizes and plumbing architecture (A don't know the confidence level that comes with using vacuum blocks and the added volume).
The lower actuator nipple opens the vanes to support exhaust flow during vacuum conditions while the upper actuator nipple opens the vanes during boost control.
As a test, run a vacuum line directly from the intake to the upper actuator nipple to eliminate the all of the solenoids, the vacuum line plumbing and isolate the test to the actuator and turbo.
This will also indicate what the "minimum attainable boost" is for the turbo.
The production units were all over the place... 8-9psi is a desired result during this test while 10-12psi can be realized on poorly built units.

[kuzman83]

Good to know, I will try that. The car does have the cat removed by the previous owner, muffler however is stock.

[cordes]

Good to know, I will try that. The car does have the cat removed by the previous owner, muffler however is stock.

That's a huge bonus. I'll be trying very hard in the coming weeks to make my CSX play nice with the boost. We'll see if I can tame it for this year. If I can it'll be incredible.

[kuzman83]

Update here. The turbo has left the building..... once I got all my vacuum lines figured out it was running great. I was driving it almost daily for 3 or 4 weeks with no problems until the turbo started acting funny. It would boost to the moon but the car wouldn't go anywhere. Seemed like it was loading up on boost as if the vanes were getting stuck, then I'm assuming the vanes would blow open because the boost would drop to about 10-12 and the car would take off.....quite violently. After horsing around with it for a few weeks I cut bait and threw on a ported t2 head with ported manifolds and a t2 turbo. Sending the comp. To Cindy this week. I saved all the vnt items in case someday I become bored and decide to crack Pandoras box for 2xx horsepower, but I don't see that happening anytime soon. T2 for now. Next up is a little body work and cutting my teeth in a paint booth. Wish me luck!