1989 Ford Mustang GT - Episode 2: Compression and Fuel Pressure Testing

Before we jump straight into troubleshooting our rich running condition in the 1989 Ford Mustang GT, we need to establish a healthy baseline for our stout little 5.0. Up first, we will be checking the engine's compression numbers across all eight cylinders to see where this powerplant stands. Secondly, we will be checking fuel pressure at the rail to ensure our pump and regulator are functioning correctly in delivering the correct fuel pressure to the rail. Lets put on our testing caps today and get in the garage and get some work done. #fordmustang #mustanggt #foxbody

[@andydhillon1977]

I enjoy this project series do much, I've got Vanilla Ice playing in the background, wearing my Z. Cavariccis, Varnet sunglasses, and ordered a Oakley Thermonuclear Protection neon green Windshield banner sticker for one of my cars! Can't wait for the next video. I'm sure it will be...To the Extreme! Get it?!!

[@autoobsessivegarage]

Haha I do everything “To the Extreme” my friend. Still have that cassette tape kicking around somewhere.

[@andydhillon1977]

@@autoobsessivegarage Word?!! Word to yah mutha!

[@camtwo1466]

The base fuel pressure KOEO is exactly 39psi for a 5.0 Mustang...Any higher and it will mess with your fuel tables and it appears that youre not using the stock MAF either which will mess with your MAF voltage to AirFlow calibration... Do you have the EGR deleted aswell?.If so and you didnt do the delete mod your timing will not adjust...

[@autoobsessivegarage]

Spot on. It’s my buddy’s Mustang, and it’s got some mods for sure…it also had a bunch of parts just thrown at it by the last mechanic to get in there. He ended up getting a basic tune to account for these mods after I set everything up to a solid baseline and the car runs great now.

[@trailerpark187]

So my 91 has a running pump but will not build pressure until it's running. KOEOi get zero fuel pressure. I can hear the pump running and the engine does run. But once it's running the pressure will be around 35psi with the regulator hooked up and 40 unhooked. But when I shut the car off the pressure drops to zero immediately. Any help would be appreciated.

[@autoobsessivegarage]

Sometimes in can be an issue with the regulator or the pump itself. For the pump, it could either be a leak on one of the hoses or maybe the check valve could have an issue. How old’s the pump?

[@trailerpark187]

@autoobsessivegarage I'm assuming original. I have a 255 pump to put in anyway. I just changed all 8 injectors and put in a known working regulator after I asked this and it's still doing it. So I'm gonna drop the tank

[@trailerpark187]

The fuel pump was not original. The pump is a walbro. Not a 255 pump. But I found a small weeping leak on the tank.

[@Jonathan-fx5pr]

That’s definitely your fuel pump on it’s was out

[@24theMoney]

Never knew the fuel pump relay is under the seat.

[@autoobsessivegarage]

Pretty wild right?

[@Jonathan-fx5pr]

Not in 93’s. Under the hood.