74 XLS 1996 Crusader

"The 7.4 is fuel injected thro

"The 7.4 is fuel injected through the throttle body. I have replace all the fuel filters and keep the fuel maintained with Staybil. The other engine runs fine but for some reason the port engine will not throttle past 3000 rpm. Once you reach that rpm the engine no longer runs smooth and will no longer keep up with the other engine.. I have replaced the plugs, plug wires, dist. cap and button, clean air filter. Nothing has worked. Is there a sensor that might be throttling back this engine. I did also check with a timing light to make sure the engine advances when reved. It is advancing.
I read a few things about the anti siphon valve but cant find it. Any advice would be great!!"

"First step after you have che

"First step after you have checked the linkage, plugs, wires and filters is a fuel pressure test followed by a compression test.

If you have an anti-siphon issue it will show up in the fuel pressure test under a load.

If you don't have the service manual, get it. That will detail the pressure specs as well as lay out other troubleshooting steps you may need to follow.

Good luck
Rick"

Thanks Rick. Compression has

Thanks Rick. Compression has been tested when I purchased the boat and it was great. The engines have 390 hrs on them. Is the fuel pressure test something I can do on my own or do I need to hire someone to come out and check?

"All you need is a fuel pressu

"All you need is a fuel pressure gauge with the appropriate adapter. Some auto parts stores will loan or rent them. Suggest you get a newer version, one with the pressure relief valve and the drain hose."