Frequently Asked Questions

D Jet Fuel Injection

 March 02, 2011 10:11 PM

Subject: 1970 volvo p1800e

Thanks for your quick reply and the information about FI systems et al.  Now I'd like to ask another question:  Ever since I got the car it has exhibited a 'stumble' or 'hesitation' that has at times gotten better, and at times gotten worse.  Gazing into your crystal ball, do you think this is likely to be a fault in the 'brains' of the FI system, wiring, a simple pinhole leak somewhere, or would I be better off simply switching to a carburetor?  Also, with a supercharger system w/carbs, is altitude ever a problem?
Brian Hatfield
Very difficult to diagnose long distance though I can offer a couple of suggestions.
1) assuming that you have the original vacuum retard distributor - disconnect the vacuum retard and plug the hose from the manifold. Try it like that, and then try it with more mechanical advance. The car should really have a vacuum advance distributor as they had everywhere except the US. Your distributor bushings may also be worn, throwing off the timing.
If the rotor and shaft have any side to side play, then the bushings are wornout.
2) Assuming that its a lean stumble, then the only easy way to richen the mixture ( and the lean condition could be caused by any number of factors in the FI system, its wiring and sensors ), try increasing the fuel pressure.
As to carbs on a supercharger and altitude - its no more of a problem then on a normally aspirated engine with carbs.
They do not adjust automatically to large changes in altitude, while a modern FI system will.
Hope this helps.
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