90 civic dual point FI problem

Anyone know how to troubleshoot a 90 1.5L with dual point fuel injection? Will only start and run with secondary fuel injector disconnected. Otherwise floods out and won't run. No trouble codes unless injector is unplugged. Neither injector seems to leak only spray while engine is cranking. Tried all the tips in the Haynes book and all voltages and resistances seem OK for the injectors, MAP, temp sensor, air controller, etc. Any other ideas? Thanks

Reply to
Mike McDonald
Loading thread data ...

secondary may be sticking open much longer than required. can you start the engine with secondary disconnected, then reconnect once running? if so, does it run ok or flood again? the secondary should not [or hardly] be injecting at idle, only on enrichment. if you can see it throwing fuel, with the engine warm at any rate, it's sticking open.

on a related matter, is the tandem valve opening ok? check it by disconnecting the tube on the diaphragm, opening the tandem valve [that's the "choke"-like thing at the top of the throttle body] and putting a wetted finger over the diaphragm inlet. the tandem valve should stay open. if it closes, the diaphragm's shot. that's uncommon. much more likely is that the vacuum tube from the actuator is leaking. simple & cheap to replace about 1.5".

Reply to
jim beam

Reply to
Mike McDonald

that's good, but clicking != guaranteed correct function.

the best check is to get a scope & look at the signal. if it's the same as a functioning dpfi civic, it's not the ecu, but it's not likely to be the ecu anyway.

ecu will almost certainly set a code on the map sensor [or ap sensor in the passenger cabin] being defective.

if you hold the tandem open while you're running the engine, you'e going to have a problem - it works /with/ the auxillary injector to make sure there's sufficient vacuum to vaporize the fuel. no restriction from the tandem = no vacuum = "excess" fuel.

btw, what symptoms make you think it's flooding? if it's simply not starting, check the main relay. your vintage civic is a prime candidate for this very common problem.

otherwise, get yourself to a junk yard & get an auxillary injector. they rarely fail, so a used one is likely to work just fine - at least good enough to get a decent diagnostic.

Reply to
jim beam

Reply to
Mike McDonald

i sympathize, but you're caught between the rock & hard place of not having more extensive test equipment & not wanting to unnecessarily replace parts. if you don't have the gear, you got to replace parts. all you need is a used injector. it's not that expensive. poke about your local junk yard.

Reply to
jim beam

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.