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740 to 240 engine swap 700 1990

Due to a thrown rod in the original 1990 740 turbo engine I have replaced it with one from an 89 240 non turbo. No problem hooking it up since the engines are almost identical, however, it doesn't want to run over about 15 to 30 minutes at a time. It also requires priming with fuel prior to starting each time indicating that the cold start valve is not working.

I have placed a pressure gauge on the fuel rail and it will hold fuel pressure for well over a week if untouched, so I consider that to not be the problem. The injectors are obviously firing as the raw fuel charge would not last 20 to 30 minutes otherwise. A noid on the injectors indicate that they are working.

If it is getting fuel and fire then why is it not working. Though I have changed the computer it is still out of another 740. I also changed the EZL controller, but it will only work with the original.

I am not new to oddball engine swaps having installed a straight eight Buick engine into a 1942 Dodge convertible, and a 3.8 V6 into a Chevrolet Monza with an original 4-cyl. But all of those were carbureted engines. I have owned and repaired Volvos from the 122S to the 1800S, to the present 740/240 situation.

Has anyone run into this problem before? What is the secret of success? I would like to exhaust all possibilities before pulling that 240 engine out and replacing it with something else.








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    740 to 240 engine swap 700 1990

    I'm not sure if it's a really good idea to put a non turbo engine into a turbo car. The engines have different pistons. Putting a flat piston higher compression engine in a turbo car risks predetonation and more thrown rods.








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    740 to 240 engine swap 700 1990



    Are you still running the turbo on the 240 motor? If so, dial back the boost a little (via the waste gate).

    Did you swap over all of the sensors between engines? They should be identical, but you never know what someone did to an engine before you got it.

    I'd put the car back to how it was electrically.... then troubleshoot from there. The turbo computers should run the NA engine. They should also give you a little insight via the OBD codes (check the 700/900 FAQ for how to get them - no tool needed).

    What's the fuel pressure? Since you have fuel and spark, it's got to be a mixture thing. I think I'd suspect a coolant temp sensor or AMM. Is the turbo plumbing 100% good... without vacuum leaks?

    -Ryan








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    740 to 240 engine swap 700 1990

    I think there is no way to answer this without knowing which wiring and sensors you replaced or re-used. The problem is not the motor but the electronics IMO.
    90T was LH2.4, 89 I don't know if it was 2.2 or 2.4. Turbo and non ECU do not interchange. Temp sensors may not interchange. Injectors may/may not interchange as there is a resistor pack for some. Crank sensor must be working...
    2 series does not use a radio suppression/fuel injection relay, 7 series does.
    Many many other possibilities;; let us know.
    Oh, and now you have a non turbo, right? or did you put the turbo on the nonT motor?







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