Jessica Elmer

78 tpi ran fine then suddenly wouldn't crank. Fuel filter suspected and removed and discarded by my dad. Sat open for 6 years. We removed and replaced the tank ( and all interior of tank) replaced filter and when spraying carb cleaner in man runs great for a second then dies. I suspected the injectors weren't working since I couldn't seem to even flood the car. No power to injectors when volt meter tested and key on. Could this be as simple as a connector fell off or what? This was obviously the original problem the day my dad removed the filter. What is the best place to start? How do we know where the power even comes from on a mod system? Please tell me that there is a certain place the power is usually connected through in these types of mods and just where to start please!!!

TimAT

What is the manufacturer of the TPI system installed? There are several on the market. I'd also suggest checking the distributor for spark. Some of the TPI systems rely on the distributor for a signal to the injectors. (pulse)
I would also check the fuel pump. If it's not making the required pressure---

71VetteLover

I'm really confused. You say it won't crank then you say the injectors aren't spraying any fuel. You need to solve your "no crank" problem first and THEN look into the injector problem.

rebel542

I believe she might have meant start, not crank.
I'm not sure you can detect voltage at fuel injectors as it is so low and a pulse. Hard to give any advice as you also let it sit for so long. You can check injector function using a stethoscope if the engine is switched on and spinning by the starter. Touch the body of each injector with the scope and you'll hear "clicks" while the engine is spinning, if they are good and receiving a signal.
Always be careful of loose clothing and hair around a spinning engine

rebel542

I completely missed your basic question about power. On every stand alone harness I've ever seen there is a fuse block. You just gotta look for it. I hid mine in the storage compartment behind the passengers seat along with the ECM. Find that and check all your fuses.
Hope this helps.

P.S. I have TPI on my 79 that I installed myself.

Jessica Elmer

I found the ECM but no extra fuse block. im gonna test for actual function on the injectors this afternoon but I was wondering if the multimeter gets signal on 200m under v when all injectors unplugged but no signal if you plug one back in does that mean bad injectors? I mean does it mean one is grounding out once plugged back in? im pretty sure that its firing since I can get it to crank and run briefly when spraying carb cleaner into manifold. it runs until it burns the spray then dies.
I also read that the throttle position sensor on the throttle body should read .54v and if its higher it prevents injectors from working assuming flooding. not sure but im gonna go check that now

71VetteLover

What are you using for an electric fuel pump? it sounds like the electric fuel pump isn't pumping fuel. Did you mount it in the tank or are you using an aftermarket inline fuel pump mounted on the frame back by the gas tank?

tracdogg2

Tps has to be above 4.5 volts to activate clear flood mode. Only use a digital volt meter when checking the sensor, not an analog.
Buy an injector test light. It's called a "noid light
Mike"

Jessica Elmer

I have no power in my throttle body position sensor when tested with multimeter.what could that be?

Jessica Elmer

its a new fuel pump inside the tank and its working cuz I hear it and there is gas behind the pressure regulator

DUB

I know it as asked.... but I did not see where you replied on what type of fuel injection system is on this engine????

The ECM provides a 5 volt reference signal to the TPS.

DUB

Jessica Elmer

I have a tpi on a 78 corvette ran off accel spark ignition ecm 74022-a. I'm thinking now that the ecm isn't working because I have no power to the things it powers. How do I test the ecm? It doesn't have a port for a obd scanner

carriljc

I googled ECM 74022-a and it sounds like a it's an ACCEL/DFI system. Below is attached a PDF with some info/

Might want to read up on it. If it was mine I'd try to find some software and/or hardware to be able to read and access the ECM.
MEANWHILE:
I would put a timing light on any given plug just to see if it's firing while cranking.
If it is firing, then just for funsies pull a spark plug and see if it's soaked in gasoline.
I am suspecting that it is NOT getting gasoline because you said you can get it to run if you spray some into the intake.

These will be 2 quick easy checks just to see if you have SPARK and to see if you have FUEL at the cylinder.

Jessica Elmer

if it cranks when carb cleaner sprayed in throttle body then it has spark right? I don't think the ecm has power and I cant find an inline fuse. the injectors aren't bad cuz I did the click test on them and they all worked, there is no power on the throttle body position sensor or the injectors and that's all the ecm controls right? I would love to find the inline fuse if it has one and check that. any ideas on where the inline fuse would be or could they have installed without one? all of my other components are functioning. I am certain no gas is dumping because I cant even smell it

carriljc

Well, for communication purposes we need to clarify our terms:
CRANKING: is just the action of the engine turning over.
If it STARTS(runs on it's own) after CRANKING(engine turning over), then you MAY have spark --- can't be sure because you are actually spraying starting fluid in there.
Just do the 2 tests mentioned above and check to see if you really have SPARK and ALSO TO CHECK the spark plugs have fuel on them. It's relatively easy and it will answer a few questions so we can move ahead.
Do you have a fuel pressure gauge mounted?

Jessica Elmer

ok. it starts long enough to burn off the spray then dies. I do have a fuel pressure gauge.

carriljc

Also, if your ECM reacts like the typical GM ECM, then when you first turn the key to ON (not START, just ON), then the fuel pump should run for little while (20 secs, 30 secs?) and build up pressure, then fuel pump stops, until you decide to go to start and then it CRANKS over and it starts. Check and see what the fuel pressure is at the end of those 30 (or so) seconds. Typical TPI type systems should be reading about 43 psig.

71VetteLover

The fuel pump only runs for two seconds on my '82.

71VetteLover

You need to put a fuel pressure gauge on it and see what the gauge is showing while you're cranking it. It should be showing 43-45 psi while you're cranking it.

carriljc

I concur. We need to know fuel pressure.
2 seconds "could" be ok, but 2 seconds would not typically be long enough to build up fuel pressure to support engine starting (if cranking it may be enough though), on mine, with the key to "ON" it would take about 10-20 seconds and then pause, I typicallly start it like this so that I have full fuel rail pressure before going to "START"..... and, of course, I only start every week or two.

Fuel pressure reading is valuable information to support troubleshooting.