84 C4 not starting
Thread Starter
Cruising
Joined: Nov 2012
Posts: 12
Likes: 0
84 C4 not starting
OK...so I bought this car for next to nothing. Replaced the Starter and battery, drained and cleaned the fuel tank, changed the fuel filter. I have fuel pressure on key turn and on turn over. (psi not known). I have spray at TBI units. Wont start.
Tried pouring gas in carbs...fires right up.....
Any more places I should check?
And yes for all that might wonder, this IS my first..... so I am on a very large learnig curve here.....
Tried pouring gas in carbs...fires right up.....
Any more places I should check?
And yes for all that might wonder, this IS my first..... so I am on a very large learnig curve here.....
Pro
Joined: Oct 2012
Posts: 613
Likes: 3
If it doesn't start unless you pour fuel in the tb's cold be really dirty air filter, or air cleaner housing vanes closed not allowing enough air in.
Normally the way you did it would mean no fuel or not enough fuel but if the tb's are spraying then you've got fuel.
Other's will say it but
1- pull any cel codes.
2- check your timing/ignition system/fuses
3- when possible check your fuel pressure
4- change your fuel filter and hoses
5- ohm check your map sensor/make sure map sensor hose is good not cracked or plugged and on tight.
Normally the way you did it would mean no fuel or not enough fuel but if the tb's are spraying then you've got fuel.
Other's will say it but
1- pull any cel codes.
2- check your timing/ignition system/fuses
3- when possible check your fuel pressure
4- change your fuel filter and hoses
5- ohm check your map sensor/make sure map sensor hose is good not cracked or plugged and on tight.
Thread Starter
Cruising
Joined: Nov 2012
Posts: 12
Likes: 0
Well lets go with the TB's being dirty first. I cant exactly see how well the fuel is spraying, as I just put 2 shop rags under them while attempting to start it. had fuel on rags. The air cleaner was not on, so veins should not have been an issue at that moment.
So how would one clean them?
So how would one clean them?
Pro
Joined: Oct 2012
Posts: 613
Likes: 3
Well lets go with the TB's being dirty first. I cant exactly see how well the fuel is spraying, as I just put 2 shop rags under them while attempting to start it. had fuel on rags. The air cleaner was not on, so veins should not have been an issue at that moment.
So how would one clean them?
So how would one clean them?
Spray the cleaner into all the tiny orifices you see where the throttle plates rest when closed, open them and spray. This should clean them well enough to start it.
Run a can/bottle of chevron techron or seafoam in the tank to keep them clean.
Pro
Joined: Oct 2012
Posts: 613
Likes: 3
you could take the tb's off and do a good cleaning like the old days with motorcycle carbs and reg auto carbs, the tb's may need to be re-bushed you won't know until you check the play on them.
The only way to test for fuel volume is to test like shown in the video below.
This video shows the procedure.
http://www.youtube.com/watch?v=HUbsOYPoQcw
If you don't have enough volume check the fuel pressure from the fuel pump, the pump supplies volume, restrictions create pressure, fuel pressure regulator regulates how much pressure is supplied to the tb's injectors.
Race Director
Joined: Dec 2000
Posts: 17,551
Likes: 26
From: El Paso Texas
How many lbs of fuel pressure? Until that question is answered, you're just guessing. Run a T to a low pressure gauge (0-15 psi) off the pressure line just past the fuel filter. Test at key on, and with 12v jumped to terminal G on ALDL. Post both readings.
CFI needs between 9-13 psi to run. They aren't happy under 10 psi constant.
CFI needs between 9-13 psi to run. They aren't happy under 10 psi constant.
Le Mans Master
Joined: May 2006
Posts: 9,226
Likes: 9
From: Irvine Ca
^^He is spot on...the fact that your injectors spray something, and the motor doesn't run unless you poor gas into the TBs tells me that there may be the required pressure at first, but after a squirt or two, a blockage or faulty fuel pump cannot keep the pressure at the minimum and your injectors stop squirting
Look at this way, put a hose on your outside water spigot with a handle sprayer on the end........crack the spigot open, but just a little bit.....The hose fills with pressure (6psi for city water), but once you start spraying, the pressure drops and your nozzle has just a trickle coming out.....Lack of GPM.......
You have a fuel delivery issue......Fuel pressure is the way to tell when you've addressed the correct thing...but I'd wager the fuel sock on that fuel pump is the culprit or the fuel pump itself....
(Did we mention Fuel pump in an '84 thread??? Queue the 84 FP vs 85 FP debate!!)
Look at this way, put a hose on your outside water spigot with a handle sprayer on the end........crack the spigot open, but just a little bit.....The hose fills with pressure (6psi for city water), but once you start spraying, the pressure drops and your nozzle has just a trickle coming out.....Lack of GPM.......
You have a fuel delivery issue......Fuel pressure is the way to tell when you've addressed the correct thing...but I'd wager the fuel sock on that fuel pump is the culprit or the fuel pump itself....
(Did we mention Fuel pump in an '84 thread??? Queue the 84 FP vs 85 FP debate!!)
Last edited by jhammons01; Nov 21, 2012 at 10:03 AM.
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Race Director
Joined: Dec 2000
Posts: 17,551
Likes: 26
From: El Paso Texas
You have a fuel delivery issue......Fuel pressure is the way to tell when you've addressed the correct thing...but I'd wager the fuel sock on that fuel pump is the culprit or the fuel pump itself....
(Did we mention Fuel pump in an '84 thread??? Queue the 84 FP vs 85 FP debate!!)
(Did we mention Fuel pump in an '84 thread??? Queue the 84 FP vs 85 FP debate!!)
Perzactly. You have a fuel delivery issue. Once we know how many psi with terminal G jumped, we can determine if it's a flow/pressure problem, or an injector issue.You could have one or more of the follwing:
1. Faulty fuel pump and/or check valve in fuel pump.
2. Sock on fuel pump clogged.
3. Pulsator split.
4. Filter clogged, or other obstruction in pressure line.
5. Injectors clogged or faulty.
6. Faulty relay together with faulty oil pressure switch.
7. Wiring fault in fuel pump circuit.
8. Faulty ECM.
Time to start troubleshooting and narrow down which.
Thread Starter
Cruising
Joined: Nov 2012
Posts: 12
Likes: 0
Well....seems I did not have all of the water out of the tank. Pulled the sending unit and found 3/4 tank....hmmmmmmmmmm LOL plus found that top of sending unit cracked and rusted. SO......off to find a sending unit.....thanks so far for your help. I would have rather found all of this now, rather than later. And cant expect much from an almost 30 year old vette that was abused by some kids. IE......thats why the name...Frankenvette. I'll keep this updated....... Hope you all had a great thanksgiving BTW...... by next week it I will have run out of leftover recipies and will be having turkey smoothies........
After a new fuel pump, a new fuel sending unit, a filter...and blowing out the lines and some fresh gas.....she fired righ up!
