Back in a Fox

[KSSVO]

Afternoon all. Just a quick intro. A few years back, I rescued a black 86 SVO from a guy who had plans to do a TR6060/turbo 6.2 LS swap and possibly nose swap to a 4 eyed GT set up the car.

Having been around a lot of Foxes, that made my heart sad, so I bought it and brought it back to life. 99K rust free and never wrecked. It was stock down to the cat and air box. It has a 3" downpipe, cone filter, Gnari manifold, EGR delete, ported lower and hollowed upper intake now. Oh and some 95 Cobra wheels.

This makes my second 86 SVO, fifth Fox and 6th Mustang/Capri. The car is not without fault though. It has a weird fuel vacuum issue that I need to sort by dropping the tank, blowing the vent lines out and replacing the tank vent. A second issue is the car falls flat on its face at 5000rpm. On the premium setting, it pulls hard and clean and makes 17+psi but then drops to 12psi at said rpm. The rear is growly and makes locker noises on sharp turns when it warms up but I'd guess that whoever flushed it at some point didn't put friction modifier back in.

https://youtu.be/HGoKZMHDnXc?si=jshrd_pJt7VryRTT

All of my pictures are big x huge so use your imagination on what a black 86 SVO looks like. If you have one, go look at yours.

[gbeaird]

Congrats on the save and welcome!!

[KSSVO]

Resized photos. The car was a legitimate barn find. Flat tired, covered in coveted barn dust. I had to summon all my old detailing and paint prep work to make it a 20 footer.

[GAboySVO]

The falling flat a 5k rpm could be caused by a couple of things:

1. You are running out of fuel pressure, knock ensues, ECU starts pulling timing, boost drops and power drops.

2. Valve spring float.

3. Cam timing off a tooth? If the cam timing is advanced, it would hit hard down low and run out of breath at the top end.

4. A combination of all 3 above issues.

Verify fuel pressure under boost as a first step.

[KSSVO]

With the tank vacuum issue right now, my money is on fuel issue mostly. Cam might be off a tooth, having timed enough of these Limas, they're obnoxious and just about make getting an adjustable cam.pulley feel really worth it. Valve springs are possible. The car has 99K on it. It looks to have been cared for when it was on the road though. If was parked due to a popped head gasket like a lot of them. And based on it being melted between 2 and 3, I'd bet my favorite toe that if was fuel related and burned out.

I'd add the spark knock in as well but with the Gnari manifold, I deleted the EGR, so there really isn't any knock sensor short of the O2 reading really lean and dumping fuel.

[svono50]

Welcome to the forum and back into the SVO world! Car looks like a nice starting point for sure. The sudden drop in boost is either a loss of energy (i.e.- exhaust force) or a high boost leak. Sounds like your ignition flame is getting blown out, so make sure you have 'good' ignition components. Remember, our cars DO NOT like fancy spark plugs, stick with the basic copper units and gap them a little tight (~0.030"). Make sure you have a clean fuel filter and also may need to send out your injectors for a cleaning/balancing. Good luck clearing up your power.

[KSSVO]

I only ever run copper NGKs in these things. Or most things really. Even my 03 Mach 1 preferred them. All plugs are capped at .028. Fuel filter is new but the tank might have made it un-new. Coil is a Ford stamped OE part, so the typical TFI coil. It has a new Chinese TFI module in it since you apparently can't buy Motorcraft ones anymore. I've found several listings and almost all buyers report getting something not Motorcraft in a Motorcraft box.

When it decides to not be idiotically cold or snowy outside, I'll get the car in the air and poke around. Valve springs would suck as I don't really want to take the car back apart. Conversely a waste gate would suck for the very same reason.

All this and I have cooling system work to do on my KLR650 and the voltage regulator lead and rear fuel pump to tend to my the F250. Good times!

[svono50]

Keep running down the list and good luck. Sometimes issue solutions just don't want to reveal themselves to you. Hope it is something easier than harder to fix/replace when you do figure it out.

[KSSVO]

When the weather clears up a bit. I have the boost controller and tank vent sitting in it and waiting. I could try throwing a hotter coil and new fuel filter in it as well. But that sort of flies in the face of the scientific process.

It is actually sitting with a fuel gauge on the rail right now. It shows 39psi at the log with the regulator vacuum line connected. Pressure dropped to about 29-30 with the line off. So it is doing its part at least at idle.

[KSSVO]

Well. I found the fuel tank vacuum issue. The last soft line to the tank was crushed by the tank. Still has a stumble but it's not as bad. I need to verify running fuel pressure but probably time to move onto boost or spark.

[svono50]

That crushed hose could certainly create some issues when trying to move some larger amounts of fuel.

Also make sure the fuel pump switch is in working order. That is the little pressure switch in the engine compartment by the wiper motor. It reduces the voltage to the fuel pump circuit when the engine is pulling vacuum and closes when you get near boost to bring full voltage to the circuit. Apparently it was there for idle NVH of the pump. Easiest test is to hook up a hand vacuum pump to the signal line with car off to see if you can hear the relay switch cycle. At atmospheric pressure, the switch should be closed and when you apply some vacuum, the switch will open up. You can verify the switch position with measuring the continuity across the electrical terminals. I took a video showing the fuel pump pressure switch function that you can check out here if you are interested: https://youtu.be/PpEu1zkEurE?si=yzFlc6r45giQwAQX

[KSSVO]

So I had always been told that the big weird UFO looking pulse regulator on the supply line was there to sampen the injector pulse. I've never heard of a pressure switch on the firewall.

Interesting. My car is missing the fuel line pulse dampener as it was MIA when I bought it. Someone had installed a second factory style fuel filter in its place. I'd put one back but they seem to be rather hard to find and from what I've read, not really needed.

[KSSVO]

I'm a dingus. I forgot it's that one in the rubber sock.

[svono50]

I'm a dingus. I forgot it's that one in the rubber sock.

No biggie, you did actually know what I was talking about. Took me quite a while to figure out that my pump was fine, it was that it wasn't being driven with the proper voltage.

Our injectors are batch fired vs sequential, hence the reason for the dampener. I have heard good/bad things if you remove it, but never any real proof that it is 'bad' to remove it. My guess is that it helped smooth out some flutter in fuel pressure during development and Ford kept it to be 'safe' from a warranty standpoint. I wouldn't worry about it missing.

[KSSVO]

If I could find one, I'd probably throw it back on. The car actually ran pretty good today. Second full tank of actual 91 through it and I grabbed second pretty zesty and it spun second out to about 50. It's no rocket, but I think it's slowly coming to life.

Thankfully the state of Kansas is a full month behind on tag stuff, so it will just roll dirty until then. Good old bureaucracy.