I just finished adding a svo conversion to my 1987 F250 Ford Diesel. It ran fine for about a day. Today after I ran about 50 miles I switched from SVO back to Diesel and the truck quit like it ran out of fuel. I pulled the Diesel fuel line and had fuel. I then pulled the SVO line and had fuel there. Then the truck started fine and ran till I switched over to SVO. To make a long story short after running on Diesel, when I try to run SVO the system creates a vacuum and will not run or start till I open the fuel lines. You can hear the sucking sound when I pull off the SVO line. Then the truck runs fine on Diesel. Does the Injection pump create a vacuum if the pump doesn't supply enough fuel? The SVO pump I'm using is rated at 1.5 to 4 psi. After I start running on Diesel after releaseing the vacuum, the truck runs fine on Diesel. I've converted 2 Isuzu Diesels before but this problem never happened before.
Greetings to all!! I called Diesel shops, Ford dealerships and I can't remember who all trying to find out what kind of preasure the stock pump put out. I got anywhere fron 4 to 90 psi so I bought a pressure guage and checked what my stock pump put out. It put out 4 psi after the filter plus or minus 1/2 lb. I checked my svo pump and it was putting out 1 psi before and after the filter. I also replaced the filter before checking the pressure and nothing changed. I replaced the pump Saturday morning and the truck is running fine as of now. I'm not sure of the pressure rating of the old pump but the new pump is rated up to 8 psi. When I checked the pressure after putting the new pump on it showed 2 psi at first but after running about 5 miles it was pushing 5+ psi and running fine. So I guess the pump was the problem. I'm only using 1 heated tank for vegi oil. Thanks for all of your help! This is great being able to ask a question and getting answers so fast!!