TBI injectors dribbling fuel within the spray pattern

Asked by Mar 02, 2016 at 07:45 AM about the 1989 Chevrolet C/K 1500 Silverado Standard Cab LB

Question type: Maintenance & Repair

I have new .060, 4 bolt main block, eagle crank & rods, new vortec heads
w/ 2.02/1.60 valves 58cc, .500 lift springs & 1.6 Harlan Sharp roller rockers,
lunati bare bones timing chain/gear, summit cam 446/466 lift @.050
(214/224 duration), new Edelbrock TBI intake w/ 1" spacer. Rebuilt TBI and
regulator. SS shorty headers
Here is problem, I have the cone shape spray pattern, but I have a major
dribble within the center of the pattern causing the truck to barely idle and
load up.When it is first started it does OK. Here's what I have done, I have
put 3 new sets of injectors in ( so I have ruled that out), I have rebuilt the
fuel pressure regulator 3 times and even put in a new hi pressure after
market one, I have put in a new in the tank fuel pump/filter, new o2 sensor,
new TBI pigtails, new temp control sensor, new MAP sensor,new TPS, new
distributor. Only thing I haven't replaced is the ECC, some call the ECM. I
still have same problem. What am I missing.

19 Answers

44,715

Is it possible that dirt or other foreign material is getting into the injectors or throttle body? An issue like this may require the assistance of the manufacturer.

90,975

You may have to hookup a lab scope to see if the there is a problem with the injector signal or voltage, that way you could tell if it is wiring or the ECM that giving you the problem. Injector voltage must be stable.

I would like to say no, but when I installed the new fuel pump, I flushed and cleaned the fuel tank and run fuel through it before I allowed it to the TBI. This truck has practically everything new on it; except the ECM. I have retorqued the intake bolts and check for vaccum leaks (none). I have everything that has been suggested, I have spent enough money this TBI that I should have bought the Holley TBI.But like all, I was trying to save a dollar.

I built this truck for my 16 year old son, its been in the works for a year, now we have this fuel issue. I have checked the voltage not with a scope though, I have the required voltage to the injectors and they are pulsing according to the noid strobe.

66,045

Your injectors have a pulse voltage from like 5V to 8V. But this sure sounds like dirty, leaky injectors.

66,045

I know you have new injectors, I built pretty much the same motor, it took a while to get all the bugs out.

90,975

All a Noid light will do is show you pause, it can't detect a voltage drop or noise on a circuit. You might want to replace the relays as these have been known to cause some problems even though they work.

66,045

When the motor is running at idle, somehow block the fuel return line, then see how your spray pattern is.

I understand, but I tried 3 new sets of injectors hoping I kept I was just getting a bad one, but same result, I even put an adjustable fuel pressure regualtor and tried various fuel pressur settings. I have the TBI injector bolts wore out (lol). Is the relays behind the glove box.

Ok I will try that, when I block fuel line return if pattern changes, then what is recommendation.

66,045

What is the fuel pressure? Should be 9 to 13 lbs for the injectors. I put a fuel pump in my 95' for a 97' that will push 80 lbs. But the TBI injectors needs the 9 to 13 lbs pressure. Putting in a regulator in before the TBI is not accomplishing anything. I'm just thinking the regulator in the TBI is not right. I put the 650 cfm Holley TBI on mine.

90,975

I just remember a problem from way back when about a problem similar to yours, but it was only one injector, he had replace a bad lnjector to begin with but every injector he put in after that would have a drip when operating like you have, anyway to make a long story short, bore where the injector is housed got scraped just enough that it would cut the seals on a new injector and would leak fuel out the bottom causing a drip. Might be something to look into, maight not be a scrape but a worn spot in the body. The relays should be marked what they are.

1 out of 1 people think this is helpful.
66,045

That could do it definitely.

ok thanks for all your recommendations, I will try those and see what happens.

That holley TBI is like $585.00, that will be my last resort, I will try the aftermarket adjustable regulator one more time and replace the oring gaskets on the injectors and see what happens. I also just remembered a detail I left out. On the initial start when we discovered the fuel pump to be inop, I had my son pour some gas into the TBI to verify it was fuel pump, he got gas everywhere,at time, the timing was off and backfired, caught fire and burnt TBI wiring, I cleaned and rebuilt TBI, but one injector did'nt work, so rewired, and got power. Do you think that when I applied power, while wires were shorted may have done something to the ECM.

90,975

Ahh, it is possible that the fire warped the TBI body so if that is the case then even new o-rings wont help, I would try to find a good TBI body from a wrecking yard, just make sure it also hasn't been burnt.

1 out of 1 people think this is helpful.
66,045

I gather you have not drivin this yet, with a motor like you built, you may have some other issues because of the OBD1 is set to run the stock motor. I had to get a custom chip programmed for my truck, to run the TBI set-up. I figure I'm pushing 400 hp. Just let us know.

I just replaced the ECC, seemed to have helped, I was looking for a more of a mist type spray pattern, but was wrong on that part. However, I now the same spray patterns. Once I get the exhaust on it so I can hear to readjust the right side rockers, hoping problem solved. I think I am only in the 330-350 Hp range. Thanks for your input. This has been trying, this truck should last my son through school and college if he takes care of it. Thanks again and God bless.

Sounds like the ring seal at the bottom of the injector is giving you problems, I had the same problem and went and doubled up on the o-rings and problem solved.

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