1985 Corvette L98 Engine Questions
Thread Starter
Intermediate
Joined: Nov 2008
Posts: 36
Likes: 1
From: Johnston Rhode Island
1985 Corvette L98 Engine Questions
I been driving the Antique Corvette lately and did I mention the sky is falling? Geez Louise if it is not one thing, its another. Last week, my L98 stopped working as advertised -- Previously, only a single crank was required to start her right up. Lately, she has to continually crank, it smells of gas, and when she does start she putters. I took her to the Gas Station to fill her with premium fuel, I got stuck twice on the way back to head quarters. Once while going up hill another while stopping fast. Please note, since this started progressing the RPM's will not go high at all. We are talking 2400rpm, and while going uphill it decreased to 1200 and stalled. The "fast stopping" brings the RPM's to 300-400 before stalling.
Please help with any ideas. It seems I keep dumping money into this L98. Can an LT1 be dropped in? Do they sell new L98's in crate?
This corvette was left to me in my Father's Estate, in my youthful naiveté I gave away all his other cars, including two Grand Nationals (I'm still sick). Selling this one and replacing with another is not an option. Please advise, can anyone reputable rebuild this thing for a reasonable cost in lieu of buying a new crate engine?
Please help with any ideas. It seems I keep dumping money into this L98. Can an LT1 be dropped in? Do they sell new L98's in crate?
This corvette was left to me in my Father's Estate, in my youthful naiveté I gave away all his other cars, including two Grand Nationals (I'm still sick). Selling this one and replacing with another is not an option. Please advise, can anyone reputable rebuild this thing for a reasonable cost in lieu of buying a new crate engine?
Racer
Joined: Nov 2010
Posts: 496
Likes: 10
I'm no Pro but I'd check my fuel pump and go from there. Check your whole fuel system make sure the system is in good order. That includes the fuel filter and Fuel Pressure Regulator has to maintain pressure. Hope this helps.
Team Owner
Joined: Jul 2004
Posts: 28,432
Likes: 3,285
From: Hartford WI
Usual culprits. Spark and fuel
Go to a dark garage and try get it to run. If it runs, you are lucky and you can remove one plug and put in a known good plug and see if the flame is blue. Do it for a few plugs to be sure.
Check fuel pressure and see what it is when you turn it on without the crank. See how long it holds. Before that, check the fuel pressure regulator hose. Remove it and see if it smells of gas.
Let us know what you find. In the meantime, get a Factory Service Manual or FSM and get a SCANNER. SCANNER and NOT a Code reader which is a glorified paperclip
Go to a dark garage and try get it to run. If it runs, you are lucky and you can remove one plug and put in a known good plug and see if the flame is blue. Do it for a few plugs to be sure.
Check fuel pressure and see what it is when you turn it on without the crank. See how long it holds. Before that, check the fuel pressure regulator hose. Remove it and see if it smells of gas.
Let us know what you find. In the meantime, get a Factory Service Manual or FSM and get a SCANNER. SCANNER and NOT a Code reader which is a glorified paperclip
Race Director
Joined: Feb 2004
Posts: 11,032
Likes: 2,587
From: Del Boca Vista FL
Concur with fuel pressure regulator as most likely culprit. You also have ninth injector for cold start if system is stock. If it is dirty/sticking that could account for your gas smell due to over fueling.
Check vacum to regulator and regulator diaphraghm.
Check vacum to regulator and regulator diaphraghm.
Thread Starter
Intermediate
Joined: Nov 2008
Posts: 36
Likes: 1
From: Johnston Rhode Island
Thanks guy!
The spark plugs was replaced along with new acdelco wires. I did not replace the cap or rotor. The fuel pump was replaced years ago, and would grind at times. The Fuel Filter was just changed a month or so ago. I did purchase a pressure gauge, so I can check that during daylight. I have the shop manual, and will have to look into the fuel pressure regulator as I am unaware where that is located. I will also need to lookup where/how to check the vacum to regulator and regulator diaphragm. This sounds promising. I appreciate your pointers, you guys are my goto resource! I'll let you know how I make out
The spark plugs was replaced along with new acdelco wires. I did not replace the cap or rotor. The fuel pump was replaced years ago, and would grind at times. The Fuel Filter was just changed a month or so ago. I did purchase a pressure gauge, so I can check that during daylight. I have the shop manual, and will have to look into the fuel pressure regulator as I am unaware where that is located. I will also need to lookup where/how to check the vacum to regulator and regulator diaphragm. This sounds promising. I appreciate your pointers, you guys are my goto resource! I'll let you know how I make out
Safety Car
Joined: Aug 2009
Posts: 3,751
Likes: 276
From: Melbourne, Victoria, Australia
Thanks guy!
The spark plugs was replaced along with new acdelco wires. I did not replace the cap or rotor. The fuel pump was replaced years ago, and would grind at times. The Fuel Filter was just changed a month or so ago. I did purchase a pressure gauge, so I can check that during daylight. I have the shop manual, and will have to look into the fuel pressure regulator as I am unaware where that is located. I will also need to lookup where/how to check the vacum to regulator and regulator diaphragm. This sounds promising. I appreciate your pointers, you guys are my goto resource! I'll let you know how I make out
The spark plugs was replaced along with new acdelco wires. I did not replace the cap or rotor. The fuel pump was replaced years ago, and would grind at times. The Fuel Filter was just changed a month or so ago. I did purchase a pressure gauge, so I can check that during daylight. I have the shop manual, and will have to look into the fuel pressure regulator as I am unaware where that is located. I will also need to lookup where/how to check the vacum to regulator and regulator diaphragm. This sounds promising. I appreciate your pointers, you guys are my goto resource! I'll let you know how I make out
Check you fuel pressure regulator, if the diaphragm splits fuel can go through the vacuum hose to engine.
Check the oil for gas smell, are the vacuum lines dry.
There is nothing wrong with an L98, the 85 even has TRW forged pistons standard and should do around 200,000 miles before needing to be freshened up, I ran 9psi boost on my 85 for 8 or more years.
I replaced it at 170,000 miles for a 383 engine but the L98 could have done many more miles.
Team Owner
Joined: Jul 2004
Posts: 28,432
Likes: 3,285
From: Hartford WI
My 91 didn't crack 100K before it started making a lot of noise the KS took for knocking. Calmed down when we put the thickest oil and some sort of "Motor Honey" or other thickening agent. On my Vette, I wasn't at 100K and it wasn't that good in compression either.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 764
get a FSM if you don't already have one, and start with the basics - FUEL, ignition, etc.. DO NOT start throwing parts at it without proper diagnostics. are the basic service items - air cleaner, plugs, wires, cap and rotor, all in good working order?
any codes? how old is the fuel filter? fuel pressure test - key on, 42psi - drop to 37 after 2 seconds? any fuel at the fuel pressure regulator vacuum line? second guessing here, but i'd start with the fuel system. start with the fuel pump, and work you way back. pay special attention to the FPR. if everything checks out OK, move on. double check all vacuum lines. pull the throttle body and give it a thorough cleaning. pay attention to the IAC valve and TP sensor. is the emission system intact (smog pump, cat, EGR valve, etc.)?
any service history? how many miles on that 85? with proper care, the L98 should be good for 300K, so I wouldn't even think about replacements engines at this point. sort through the issue, or issues at hand - remember, that puppy is 30+ years old. good luck - keep us posted.
any codes? how old is the fuel filter? fuel pressure test - key on, 42psi - drop to 37 after 2 seconds? any fuel at the fuel pressure regulator vacuum line? second guessing here, but i'd start with the fuel system. start with the fuel pump, and work you way back. pay special attention to the FPR. if everything checks out OK, move on. double check all vacuum lines. pull the throttle body and give it a thorough cleaning. pay attention to the IAC valve and TP sensor. is the emission system intact (smog pump, cat, EGR valve, etc.)?
any service history? how many miles on that 85? with proper care, the L98 should be good for 300K, so I wouldn't even think about replacements engines at this point. sort through the issue, or issues at hand - remember, that puppy is 30+ years old. good luck - keep us posted.
Drifting
Joined: Feb 2008
Posts: 1,537
Likes: 177
From: NE Ohio
2024 C4 of the Year Finalist - Unmodified
Thread Starter
Intermediate
Joined: Nov 2008
Posts: 36
Likes: 1
From: Johnston Rhode Island
Thanks for the response everyone, I have been met with some success! After the majority concurred with fuel being the cause, I went ahead and ordered a new ACDelco Fuel Pump, I also needed to order a new ACDelco Fuel Pump Strainer.
The repair went well and lasted around two hours mostly spent on wire-brushing the filthy assembly. Upon completion, she fired up one crank! Although the torque has increased, when flooring the peddle on the highway gas can be smelt. -- I feel there must be a vacuum leak as eluded by some members.
In an attempt at getting this conveyance to one hundred percent by solving the problem previously indicated, I hope to replace the hoses connected to the diaphragm and the fuel pressure regulator.
Any additional comments will be appreciated with emphasis on gas smell when fully accelerating, low RPM while stopping rapidly which may cause a stall, couple that an intermittent irregular idle. Thanks in advance.
Below please find the recorded process taken for ones viewing pleasure.
The repair went well and lasted around two hours mostly spent on wire-brushing the filthy assembly. Upon completion, she fired up one crank! Although the torque has increased, when flooring the peddle on the highway gas can be smelt. -- I feel there must be a vacuum leak as eluded by some members.
In an attempt at getting this conveyance to one hundred percent by solving the problem previously indicated, I hope to replace the hoses connected to the diaphragm and the fuel pressure regulator.
Any additional comments will be appreciated with emphasis on gas smell when fully accelerating, low RPM while stopping rapidly which may cause a stall, couple that an intermittent irregular idle. Thanks in advance.
Below please find the recorded process taken for ones viewing pleasure.
Last edited by JPSilvaggio; Oct 13, 2016 at 09:14 AM.
Oil Producer
Joined: Apr 2014
Posts: 9,368
Likes: 2,735
have you checked the fp regulator yet?
Thanks for the response everyone, I have been met with some success! After the majority concurred with fuel being the cause, I went ahead and ordered a new ACDelco Fuel Pump, I also needed to order a new ACDelco Fuel Pump Strainer.
The repair went well and lasted around two hours mostly spent on wire-brushing the filthy assembly. Upon completion, she fired up one crank! Although the torque has increased, when flooring the peddle on the highway gas can be smelt. -- I feel there must be a vacuum leak as eluded by some members.
In an attempt at getting this conveyance to one hundred percent by solving the problem previously indicated, I hope to replace the hoses connected to the diaphragm and the fuel pressure regulator.
Any additional comments will be appreciated with emphasis on gas smell when fully accelerating, low RPM while stopping rapidly which may cause a stall, couple that an intermittent irregular idle. Thanks in advance.
Below please find the recorded process taken for ones viewing pleasure.
The repair went well and lasted around two hours mostly spent on wire-brushing the filthy assembly. Upon completion, she fired up one crank! Although the torque has increased, when flooring the peddle on the highway gas can be smelt. -- I feel there must be a vacuum leak as eluded by some members.
In an attempt at getting this conveyance to one hundred percent by solving the problem previously indicated, I hope to replace the hoses connected to the diaphragm and the fuel pressure regulator.
Any additional comments will be appreciated with emphasis on gas smell when fully accelerating, low RPM while stopping rapidly which may cause a stall, couple that an intermittent irregular idle. Thanks in advance.
Below please find the recorded process taken for ones viewing pleasure.
Team Owner
Joined: Jul 2004
Posts: 28,432
Likes: 3,285
From: Hartford WI
Thanks for the response everyone, I have been met with some success! After the majority concurred with fuel being the cause, I went ahead and ordered a new ACDelco Fuel Pump, I also needed to order a new ACDelco Fuel Pump Strainer.
The repair went well and lasted around two hours mostly spent on wire-brushing the filthy assembly. Upon completion, she fired up one crank! Although the torque has increased, when flooring the peddle on the highway gas can be smelt. -- I feel there must be a vacuum leak as eluded by some members.
In an attempt at getting this conveyance to one hundred percent by solving the problem previously indicated, I hope to replace the hoses connected to the diaphragm and the fuel pressure regulator.
Any additional comments will be appreciated with emphasis on gas smell when fully accelerating, low RPM while stopping rapidly which may cause a stall, couple that an intermittent irregular idle. Thanks in advance.
Below please find the recorded process taken for ones viewing pleasure.
The repair went well and lasted around two hours mostly spent on wire-brushing the filthy assembly. Upon completion, she fired up one crank! Although the torque has increased, when flooring the peddle on the highway gas can be smelt. -- I feel there must be a vacuum leak as eluded by some members.
In an attempt at getting this conveyance to one hundred percent by solving the problem previously indicated, I hope to replace the hoses connected to the diaphragm and the fuel pressure regulator.
Any additional comments will be appreciated with emphasis on gas smell when fully accelerating, low RPM while stopping rapidly which may cause a stall, couple that an intermittent irregular idle. Thanks in advance.
Below please find the recorded process taken for ones viewing pleasure.
Team Owner
Joined: Jul 2004
Posts: 28,432
Likes: 3,285
From: Hartford WI
Team Owner
Joined: Jul 2004
Posts: 28,432
Likes: 3,285
From: Hartford WI
Safety Car
Joined: May 2001
Posts: 4,755
Likes: 1,644
From: Fairfax Virginia
Todays Gasoline
I would replace any critical parts with rubber including diaphragms, because of exposure to the Ethanol that is in our gas. Once they are exposed to 10% Ethanol they start breaking down and their reliability goes out the window.
Thread Starter
Intermediate
Joined: Nov 2008
Posts: 36
Likes: 1
From: Johnston Rhode Island
Please tell me what to do, I can then amend and re-upload video for those experiencing the same problem in the future.