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

 

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".

 

Thanks,
Reconnecting the secondary does cause engine to reflood. I checked the
injector out of car with a nine volt battery and it clicks OK. When in car,
it does
not leak when fuel line comes up to pressure, only when engine cranking or
running,
which makes me wonder if ECU is telling it to open. With other older FI
systems I've
worked on, the MAP sensor had the ability to stop the engine from starting
or running
by making the mixture go too rich. Would like to be able to verify MAP is OK
or not
to isolate problem to the injector. Voltages to the MAP connector OK, but
there is no
test given to test the MAP by itself. Don't get a trouble code for the MAP,
but don't know
if the ECU would set one or not. No reason to suspect the ECU is bad at
this time, and they
are usually the least likely to fail. Was wondering if there seemed to be a
history of either a
FI sensors going bad or injectors failing before I resort to replacing
parts. Will check the
tandam valve, mostly I'm holding that open manually to see down the barrel.

 

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.

 

Thanks again. Will check out main relay, but since car will start when the
plugs and throttle body are dry and secondary injector is disconnected, I
doubt its bad. Could check signal to injector, but don't know what a proper
one should look like. Simple DC check shows its not always on and in range.
~5 volts I think last time I checked. Voltage to air injector OK and its
resistance OK also. If I don't come up with anything new, I guess I'll
start with a new injector and see what happens. Hate to start replacing
parts without knowing they're bad as it can get real expensive real fast.

 

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.