i own a 78 so i usually post in the c3 section but i have a tpi in another car & i really need some help. this injection is mounted on a 300 horse 350- mild build w/less than 500 miles. i am using a 1227730 ecm w/speed density fuel metering calibration & a painless wiring harness. i have had an intermittent problem for awhile now. a month ago i noticed a miss & found that i could remove #4 injector wire without changing the engines idle- like a dead miss but when i drove it at off idle & at 60mph the miss went away. now it is missing at all rpm's- still idles & still runs but sounds ragged. the injector wire shows a pulse but i do not know how to check it w/an ohm meter. a month ago the plug was wet so i replaced it & it ran somewhat better. now the plug is dry & tan & ALL plugs have a strong spark to ground. last night the injector made a tapping sound & i could feel it tapping as it pulsed- not so w/the other 7. this system is mostly all new- w/500 miles onit- new venom injectors, new wiringnew dist. module, new plug wires. i understand its not a corvette but the tpi system is almost identical & i REALLY need the help. i know there's a tpi guru out there just like lars is to the quadrajet carb.please help me if you can. am i looking at a bad injector here? on all other injectors the engine responds negatively wgen i remove the injector wire but as i mentioned NO response when i remove #4 inj. wire. can someone tell me how to check the pulse signal on the inj. connector? i have a really good auto x-ray comp. signal reader & there are NO codes on this problem. any help would be greatly appreciated. i have another tpi set-up that i planned to use on my 78 but if if i can't solve a problem like this i'd be better off w/a carb. thank you.

 

Ohm test the injectors to see if all within spec
http://forums.corvetteforum.com/c4-t...injectors.html
http://forums.corvetteforum.com/c4-t...injectors.html
http://www.youtube.com/watch?v=_g8PdrT0MCU

 

Ohms test each inj and do it hot and cold. Your single that seems to be at the center of this sounds like its not operating..even if the coil is ok its still not spraying well...This system stays HOT always and the ecm completes the ground in the ecm for each bank to fire. Older EFI were always bank fire...when one fires they all fire on that bank. Ground path is how the inj knows to fire.

Its just a bad injector..no prove it so you can fix it. Leave the inj cap on and pull that spark plug wire...see if that makes much difference.

 

The way to test injector pulses is with a "noid" light, like this one:

http://www.amazon.com/OTC-7602-Port-...662775&sr=1-14

All 8 injectors fire at the same time so if some are firing then all of them should be firing. You could have a bad connection in the injector connector or the injector itself could be bad.

The best way to check an injector is to measure the resistance of the injector coil. It should be roughly 16 ohms. You really should measure ALL of them. If one has failed, sometimes others fail as well.

Sometimes they fail when hot, so it's best to test them hot, but checking them cold first will at least give you an indication of what's happening.

 

many thanks to rodj, leesvet, & liff for taking the ime to study my problem. i learned how to ohm my injectors & found cole in atlanta- fuel injector connection. i seldom cut corners on a build but in this case i did buying the cheapest injectors on the market. i bought a set of premium inj. from cole & have my old ones out ready for theinstall. if that dosen't fix the problem i'll come back & ask for a little more help. thanks again. lonebull

 

that was cliff i was thanking not liff! sorry about that- this computer is confounding me!!