Topic: 82 CFI starts to sputter around 2K RPM
in Forum: C3 Engines
Already a Member?
Click Here to Login
Not yet a Member?
Click Here to Register for Free!
My 82 seemed to be running great until I decided to fix the cruise. Now I cannot get it to run correctly. Only thing I did was disconnect hoses from the canister on the side that goes to the PVC and tank vent. Think I have everything hook back up correctly now.
My problem now is that once I try to drive the car acts like the fuel is being shut off at around 2K rpm (not every time though) and I have to pump the throttle to keep it running. Spits and sputters until I get enough fuel back to keep it running. I disconnected the vacuum line that went to the cruise and have it plugged off now (no change). Have checked the other vacuum lines and they seem to all be ok. Have plugged the vacuum line to the headlight and interior temp control (no change). Car seems to idle a little higher than normal now and also surges every once in awhile at idle.
Fuel filter was changed about two years ago and also have an 85 pump installed. Have not measured the fuel pressure but it was around 14psi the list time I checked. Will look into this once I find my pressure gauge. Have sprayed carb cleaner around the manifold lid and don't seem to have a leak.
Any thoughts on what else I should look at. I hate when you try to fix one thing and create another problem. Car ran great before I messed with the cruise, just came back from a 200 mile trip the weekend before.
SPONSOR AD:: (Our Sponsors help support C3VR)
Lifetime MemberLemon Grove, CA - USA
Joined: 10/17/2007
Posts: 2041
Vette(s): 1982 C3 Collectors Edition 44000 miles, sat in the sun most of its life, My wife purchased it for me for Father's Day in 2007 from her girlfriend that had it for 19 years. It is on the road again. I'm retired but it is now my daily driver.
The fuel pump would have been my first guess. But a 85 pump would have taken care of that issue unless it failed which is not likely.
Something bad got into your filter would be my next guess. You are getting fuel but not enough volume it would seem you are saying.
Did you replace the sock when you replace the fuel pump. I sure you did but if you did not it could be clogging the input.
Fuel sock was changed. Little more information today
Checked the fuel pressure and was getting about 11.5 psi (was haigher the last time I checked). What is happening is suddenly it dumps a bunch of fuel and the pressure drops slightly. It then continues the sputter by dumping a bunch of fuel until it kills the engine. Each time I tried to restart the fuel pressure was a little lower until it was running at 9 psi. Tried to adjust the fuel pressure up but could not. Actually, dropped to about 6 psi at idle.
Took the TB regulator off and the spring inside is compressed all the way and will only allow you to increase the spring pressure. Not sure which way to go to get it to fuel pressure to increase?
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Shawnee2 said:
Checked the fuel pressure and was getting about 11.5 psi (was higher the last time I checked). What is happening is suddenly it dumps a bunch of fuel and the pressure drops slightly. It then continues the sputter by dumping a bunch of fuel until it kills the engine. Each time I tried to restart the fuel pressure was a little lower until it was running at 9 psi. Tried to adjust the fuel pressure up but could not. Actually, dropped to about 6 psi at idle.
Took the TB regulator off and the spring inside is compressed all the way and will only allow you to increase the spring pressure. Not sure which way to go to get it to fuel pressure to increase?
When you say "dumps fuel", do you mean the engine is running super rich, or is it running out of fuel at the infectors?
I would not try to adjust the pressure regulator to solve this issue.....I would suggest first a check of the fuel filter.
Strange that this issue just started after moving some vacuum lines for the cruize control. A loss of vacuum for the fuel regulator would increase fuel pressure.
Joel Adams
C3VR Lifetime Member #56 
My Link 
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
System shoots a bunch of extra fuel into the TB's. Will do this until it floods the engine out and stops. Fuel pressure between the TB's seems to be low for some reason. Will disconnect all the vacuum lines that I can and see if that helps any and then seperatly start to install them back
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
If the infectors are dumping that much fuel, that will explain the lower than "normal" fuel pressure. Either the infectors are leaking, or the ECM is holding them open far too long for some reason. Have you tried to get any codes out of the system that would point to a place to start?
A quick check to see if the infectors are leaking is to remove the air cleaner, and look down into the TB bores, while someone turns the key on(do NOT crank/start). If they are physically leaking, you will see fuel drip/dump out.
If you have a timing light, hook it up, and point it at the infectors while the engine is running. You should see a nice, clean "fan" spray on good infectors with proper fuel pressure and ECM control. If you see splotchy drips, your problem is not fuel pressure related....it is infector/ECM related. A failing coolant temp sensor can cause the ECM to put too much fuel thru the infectors, since it thinks the temperature is cold. I would suggest checking for codes...
A quick check to see if the infectors are leaking is to remove the air cleaner, and look down into the TB bores, while someone turns the key on(do NOT crank/start). If they are physically leaking, you will see fuel drip/dump out.
If you have a timing light, hook it up, and point it at the infectors while the engine is running. You should see a nice, clean "fan" spray on good infectors with proper fuel pressure and ECM control. If you see splotchy drips, your problem is not fuel pressure related....it is infector/ECM related. A failing coolant temp sensor can cause the ECM to put too much fuel thru the infectors, since it thinks the temperature is cold. I would suggest checking for codes...
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Finally had a chance to get back to this. Fuel pressure is way low between the TBI. Keep trying to adjust the pressure upwards at the regulator but can only get to about 10-11 psi. Adjusting screw will not go any higher. I have cappped off all the vacuum lines except going to the transmission. Car will run but will surge an extra amount of fuel into each TB every once in a while. Spraying carb cleaner does not indicate any leaks anywhere.
Any advise on how to get the fuel pressure higher. Pump is the 85 style but have not actually measured the inlet pressure yet. I have put a new regulator kit one the TB's
Former Member
Send PM
Phoenix, AZ - USA
Joined: 6/12/2011
Posts: 139
Vette(s): 1982 corvette crossfire production numer C5101985. Color is silver and claret. All original numbers match. slight mods to crossfire for better efficiancy and power balanced and added fuel pressure assembly between throttle bodies,
Maybe a bad fuel pump, fuel filter (s), or maybe an injector is clogged and or bad.
just my two cents
|UPDATED|6/28/2014 9:18:27 PM (AZT)|/UPDATED|
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Shawnee2 said: I have capped off all the vacuum lines except going to the transmission.
Any advise on how to get the fuel pressure higher. Pump is the 85 style but have not actually measured the inlet pressure yet. I have put a new regulator kit one the TB's
No vacuum to the trans on an '82 to begin with. Shift feel/timing is controlled by a cable from the TBI.
It's starting to sound like you may have a bad fuel pump, or there's something really screwy with the regulator.
Perhaps the fuel pump is not getting a full 12v while running. A loose/corroded connector can cause that. It may show 12v on a static test, but the voltage could drop under a load, with the pump running. A bad connection in the fuel pump relay could cause the same low voltage.
I think if it were me at this point, I would want to check fuel pressure before the regulator, to see what the pump is actually capable of producing.
|UPDATED|6/29/2014 9:23:06 AM (AZT)|/UPDATED|
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Lifetime MemberLemon Grove, CA - USA
Joined: 10/17/2007
Posts: 2041
Vette(s): 1982 C3 Collectors Edition 44000 miles, sat in the sun most of its life, My wife purchased it for me for Father's Day in 2007 from her girlfriend that had it for 19 years. It is on the road again. I'm retired but it is now my daily driver.
Just my two pennies. My 82 had always ran really rich. Finally it was running so rich that it would not pass smog even with a new CAT installed.
It turned out to be the temp sensor was bad it would work normally for a while then indicate cold every once in a while which confused the ECM I guess. Anyway after it was replaced the car no longer dumps fuel and passes smog easily.
That said, I would look at the fuel pump as the most likely problem.
They do not cost that much and should really put a lot more pressure out. If you replace it I would back off on your pressure regulator some before you try to start the car. I would not want to put all of the pressure an 85 pump can put out into the system.
If that does not fix it you could try the injectors. If after you replace the fuel pump and if Joel thinks it is worth a try I have a couple of newly rebuilt injectors I would loan you for testing yours to see if you need new ones. I had to purchase them when I was trying to figure out what was going on with my car. Turns out they were not the issue so I have a couple of spares that were rebuilt.
in Forum: C3 Engines
SPONSOR AD: (Our Sponsors help support C3VR)