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Username Post: 5.7 TBI injector problems        (Topic#257512)
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
02-13-11 05:58 PM - Post#2046208    

I have a 1994 K1500 5.7, I bought the truck from a friend knowing that the drivetrain had issues. The engine lacked a lot of power and had every kind of leak imaginable. After that I pulled the engine and dissasembled it down to the short block. The bores looked really nice, some cross hatching could still be seen in the bores (as far as I know it has not been bored out before) I cleaned it, painted it, cleaned the heads and valves, lubed it up good, new valve seals, new gaskets and seals all around, new timing chain, new harmonic balancer, 1" throttle body spacer, headers, new ignition module, new MSD street fire coil, 8.5mm plug wires, E3 spark plugs, Accell cap/ rotor, new starter, new O2 sensor, new computer and K&N 4" Air Charger. The injectors are fairly new and everything ran before the work started. I set my initial timing to 0 degrees as per the Chilten manual. When I try to start the engine, it will crank over and there is fuel getting to the injectors. I pulled the injectors out to verify. The injectors will not pulsate. I bought a noid light and it doesnt flash. I am in the process of checking all my grounds. I have seen several wiring diagrams for it and some have the injectors coming from the computer to the injecters then to the fuse and others have it wired into the TCC/brake switch. The fuses are good and the truck is in park. Any help will be gratefully appreciated. Thanks
1994 K1500 Z-71


 
someotherguy 
Moderator
Posts: 25635
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
02-13-11 06:41 PM - Post#2046230    
    In response to navygunner08

Welcome,

On a TBI, most common reason for no fuel spray from the injectors - although there is proper fuel pressure - is a bad ignition module. They can (and do) fail in a way that you can still have spark, but no signal to the PCM to ground the injectors.

(Of course, they also fail in a way that won't allow spark.)

Sometimes a parts house module test will show a failed module, sometimes it won't.

If you've got proper fuel pressure (9~13 psi is spec, prefer to see 10 or better) and you're not getting fuel from the injectors, suspect the module first.

Also, not a fan of aftermarket fancy plugs on a TBI - maybe you'll be OK with that MSD coil, maybe not; TBI's (and first-gen Vortecs as well) don't seem to like anything weird and that even includes "plain" Bosch Platinum. Too many documented cases of misfires with the weird plugs and running fine on the spec'd AC CR43TS.

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
02-14-11 03:59 PM - Post#2046603    
    In response to someotherguy

Thank you for replying so quickly. The ignition module was replaces shortly before the engine overhaul. The fuel pump was also replaced recently along with the sending unit. Where can I get my ignition module tested? Are there any wiring diagrams that show the proper placement of grounding wires? I am out to sea right now, so I will check these when I get back. Thank you
1994 K1500 Z-71


 
someotherguy 
Moderator
Posts: 25635
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
02-14-11 04:30 PM - Post#2046617    
    In response to navygunner08

There are quite a few grounds in the engine compartment. For a 1994 fullsize pickup, here's what I can recall off the top of my head:

Main ground from battery to stud on intake manifold, and same cable has smaller ground to inside wall of passenger fender.

Rear of passenger side head to firewall just below heater core hoses (braided strap.)

Another braided strap from same spot on firewall to passenger side front frame rail, on top.

Two pairs of sensor network grounds at the front of the engine - one usually connected on a thermostat housing stud, and one nearby it on an intake stud.

In fact, this picture is from a '94 with the 5.7:


Some auto parts stores can test your module, but a bad module can often still pass the test. Here's some more info including testing the pickup coil in the distributor, and fuel pressure: http://www.chevytalk.org/fusionbb/showtopic.php?ti...

That's a post in the 88-98 fullsize truck section; be sure to drop by and say howdy.

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
02-14-11 04:38 PM - Post#2046619    
    In response to someotherguy

Thank you, I am going to bet its a ground, because I know for a fact that my grounds are not set up that way. Is there any chance that I damaged something when I was trying to start it?
1994 K1500 Z-71


 
D.Mac 
Senior Member
Posts: 997

Loc: Ontario Canada
Reg: 03-22-03
02-14-11 04:49 PM - Post#2046621    
    In response to navygunner08

The red and white wires at the injectors should have 12V power on them with the key on. The ECM grounds the green and blue wires to fire the injectors.

Have you got spark when you turn it over?

You said you replaced the computer. You sure it's a compatible unit?
Dave MacDonald
Ontario, Canada

'66 Impala LT1/C950-,EFI,700R4,(sold 07/2011)
'12 Sonic LTZ, Turbo, M6
'07 Pontiac Solstice GXP
'06 Caddy CTS-V


 
Lynn63 
"5th Year" Gold Supporting Member
Posts: 577
Lynn63
Age: 74
Loc: Vicksburg, MI
Reg: 02-07-09
02-14-11 10:38 PM - Post#2046777    
    In response to navygunner08

Navygunner, we just spent several very cold days looking for the reason only one side of the TBI would spray. Finally discovered one wire on the ECM connector had come loose and wasn't making contact. Don't have a clue why because we only swapped the complete intake assembly onto another SBC. Like you, everything else checked out. Might give it a look. Don't remember whether it was D14 or D16.
Lynn63
63 Impala SS
07 Silverado DMax Classic
99 Venture van


Progress so far...


Edited by Lynn63 on 02-14-11 10:39 PM. Reason for edit: No reason given.

 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
02-14-11 10:43 PM - Post#2046778    
    In response to Lynn63

D. Mac- The computer part # matched when I bought it from Napa.

Lynn63- I will check those too.
1994 K1500 Z-71


 
Dale_Holley 
Member
Posts: 379

Loc: Dallas, TX.
Reg: 11-10-03
02-15-11 09:42 AM - Post#2046950    
    In response to navygunner08

Did you swap the prom over from the old ECM (or replace it with a new one)?

 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
02-15-11 06:41 PM - Post#2047172    
    In response to Dale_Holley

The Eprom is the same original one. I did try (before I took the engine out) to run a Jet performance "6-pack" chip and the it did not like that at all. It barely ran and absolutly would not move in any gear. It ran before I took the engine out.
1994 K1500 Z-71


 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
02-23-11 04:19 PM - Post#2050931    
    In response to navygunner08

OK, I still have not been able to do anything on my truck yet because Im still floating out in the deep blue ocean. I have been reading some of Grumpyvette's posts about cams being 180 degrees out. Is it possible this is my issue? When I installed the timing chain I made sure the marks on the gears lined up and turned over the engine several times to make sure that they lined up again. When I set the distributer in, the #1 cylinder was at TDC and the distributor pointed pretty darn close to the #1 point. Did I do anything wrong there?
Thanks
1994 K1500 Z-71


 
mike beck 
Contributor
Posts: 218

Reg: 05-20-10
02-23-11 05:41 PM - Post#2051000    
    In response to navygunner08

I don't know if you can nor what would happen if you installed a cam 180* out.

On the typical SBC, the dots on the gear both need to face-up with #1 at TDC, OR the dots have to face each other with #6 at TDC.

Now, when you slowly turn the engine over watch the rocker arms on #1, at some point you will see the intake rocker open and then close. Put your finger in the spark plug hole and keep rotating the engine. You will feel the air trying to push your finger out, the rotor will get closer to pointing to the #1 spark plug terminal, and the balancer will get closer to lining-up with the TDC mark.

 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
02-23-11 06:20 PM - Post#2051030    
    In response to mike beck

That could very well be my problem. When I installed the timing gear, the #1 piston was at TDC and the marks were together (Crank at noon and cam at 6 o'clock). I guess when I get back I will be taking my engine out again and fixing that problem!

Thank you.
1994 K1500 Z-71


 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
02-28-11 08:06 PM - Post#2053719    
    In response to navygunner08

Ok, I corrected my camshaft, connected the grounds and tried to fire it up. Still no injector pulsations. I rest the computer by unpluging it and pulling out the prom and then hooking it back up. Tried starting it, nothing. I have not bought a new ignition modual yet. Is it possible that the hight voltage coil killed the ignition modual?
1994 K1500 Z-71


 
someotherguy 
Moderator
Posts: 25635
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
03-01-11 09:07 AM - Post#2053959    
    In response to navygunner08

Not likely the module is bad, though new parts doesn't always mean good parts. (I thought you said earlier the module was new already?)

Did you test the pickup coil like I described earlier?

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
03-01-11 09:55 AM - Post#2053988    
    In response to someotherguy

I have not checked the pick up coil yet. The module is new, it maybe has 10 hours of running time on it. I will check the pickup coil today and I am going to doulble check all the connectors are connected all the way. When I tried cranking it over last night. It sounded different, it sounded like it was smoother.
1994 K1500 Z-71


 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
03-05-11 06:54 PM - Post#2056331    
    In response to navygunner08

Ok, the pick up coil has decent magnatism. The cam and distributor timing issues have been corrected. Still the injectors will not pulsate. I have verified everthing electrical is hooked up correctly. Any ideas?
1994 K1500 Z-71


 
Lgib 
Member
Posts: 63
Lgib
Loc: new mexico
Reg: 01-18-06
03-05-11 08:15 PM - Post#2056371    
    In response to navygunner08

Do you know if the truck has any type of vehicle anti theft device . That would disable the injectors. Just a thought.
69 Camaro 383 sb,TC 78 turbo, Holley EFI Stealth Ram, COP
60-2 crank trigger, water meth injection, TH350, Gear Venders overdrive


 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
03-05-11 08:49 PM - Post#2056389    
    In response to Lgib

No anti theft device.
1994 K1500 Z-71


 
someotherguy 
Moderator
Posts: 25635
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
03-06-11 08:39 AM - Post#2056528    
    In response to navygunner08

  • navygunner08 Said:
Ok, the pick up coil has decent magnatism. The cam and distributor timing issues have been corrected. Still the injectors will not pulsate. I have verified everthing electrical is hooked up correctly. Any ideas?


Just checking that it's still got magnetism isn't the whole test.

You may want to re-visit the FAQ in the 88-98 section and cover the part about "won't start"

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
Danny Cabral 
Member
Posts: 3405
Danny Cabral
Loc: Ellington, CT
Reg: 11-03-04
03-06-11 09:44 AM - Post#2056563    
    In response to someotherguy

  • someotherguy Said:
Just checking that it's still got magnetism isn't the whole test.


Correct, even a failed magnetic pickup coil will still have magnetism.
May God's Grace Bless You

'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, 4" lift, 35" tires


 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
03-07-11 03:39 PM - Post#2057295    
    In response to Danny Cabral

OK, checked the resistance of the pick up, it red about 800 ohms and overload for the ground. Would it be possible that my base timing is so far off that the computer cannot correct for it and there for will not run?
1994 K1500 Z-71


 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
03-11-11 01:52 PM - Post#2059830    
    In response to navygunner08

Ok, update... I was trouble shooting IAW my chilton manual. I was trouble shooting the HEI system. I had the ignition switch on, as I was unpluging the 4 pin connector on the ignition module I heard leakage from some where. It turned out to be from the injectors. I then pluged the connector back in and before it was fully seated, the injectors started to pulsate. After it was seated we tried to see if it would crank. Nothing, no spark (spark checker was hooked up), no fuel. Is the module still suspect or maybe shorted wires???
1994 K1500 Z-71


 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
03-12-11 10:37 AM - Post#2060288    
    In response to navygunner08

We took some voltage readings to see it we were getting any voltage to the pins. As you look at the connector with the clip on top, and with the ignition in the on posission, we are seeing 1 Vdc on the far right pin, and about 500 mV dc on the rest. We are thinking the connector might have corrosion in side of it from when it sat in the truck when the engine was out. Does anyone know where we can get a new connector.
1994 K1500 Z-71


 
navygunner08 
Contributor
Posts: 758
navygunner08
Loc: Norfolk, VA
Reg: 02-13-11
03-19-11 05:42 PM - Post#2064063    
    In response to navygunner08

OK, I bought a new module to test that. No luck. Is there anyway my PROM might have gone bad or been erased, I know they erase them using UV light.
1994 K1500 Z-71


 
akha 
Forum Newbie
Posts: 3

Reg: 07-21-11
07-21-11 01:17 PM - Post#2116489    
    In response to navygunner08

Anyone discover why this is all happening? I have same problem, also see it on other forums. No pulse.

 
akha 
Forum Newbie
Posts: 3

Reg: 07-21-11
07-21-11 01:38 PM - Post#2116501    
    In response to akha

Replaced coil pick up, HEI, computer, still no ground pulse for injectors.

 
akha 
Forum Newbie
Posts: 3

Reg: 07-21-11
07-21-11 08:33 PM - Post#2116651    
    In response to akha

Ok, for the next person with this issue here is what finally seemed to be the issue. Fuel pump intermittent, enough to kick in injection accelerator pump, not enough to kick in dual injectors. Replaced pcm. Disregard ground circuit from injectors as its hard to measure accurately. Fuel pump malfunction main issue. Runs, doesnt run enough. Etc.

 
morganpainter 
Forum Newbie
Posts: 34

Reg: 02-17-13
03-04-13 06:27 PM - Post#2323027    
    In response to someotherguy

ive gottn my ignition module tested at advance auto parts and it passed, the guy that i bought the truck from said the distributor pick up might be cracked but didnt know. would that have anything to do with the fuel injectors not spraying? i have fuel up to the injectors but not thru them. and i have spark at the plugs...

Edited by morganpainter on 03-04-13 06:28 PM. Reason for edit: No reason given.

 
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