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Main trouble it’s having is that it’s hard to cold after sitting overnight. Once started it cranks fine all day long. I can crank it in the morning and it will still crank fine at 5pm but the next day it’s hard to start again. Engine turns over for 3 to 4 seconds before starting.
I have done a pressure check on the fuel system after I replaced the fuel pressure regulator and fuel pump and filter. The car pressures when key is turned on but then drops as soon as the key is off. Running it holds pressure but doesn’t seem to run right. I have had all the items above replaced within the last month or so but nothing has seemed to fix the problem. My gas mileage is only about 12 miles per gallon around town and 20 on the highway. I always run premium fuel.
Parts I've replaced without any change.
Why exactly did you change all those things? Was there some reason or did someone tell you those are issues?
Check with FIC if you have Multec injectors. If you do, toss them. Multec Injectors are on the left if the pic is accurate. Mine have been tossed so long ago, I can't remember
If it isn't Multecs, send them for cleaning and testing. I do that every 3 years and there is always a flow improvement in both volume and pattern when I verify them. No the snake oils, whiffle dust, mouse milk or "cleaner in a can" is there to separate you from your money.
To the OP, I was having the same issues you are having almost to a tee. I put in the bosh 24lb injectors [blue ones in picture] and she's running better than it ever did since I have had her.
Well I started trouble shooting and one thing led to another. The evaporator canister charcoal pellets had filled the vacuum line and solenoid and the fuel pump and pressure regulator were an attempt to find the cause of the fuel rails not holding pressure. Haynes manual said if its hard to start when engine is cold it is one of those things so on and on. I have found numerous errors in Haynes manual in all kinds of areas. Then another reason for replacing all those things was pure desperation. I have Multec injectors. I went to a fuel injector shop and he says he can pull them and clean and flow test them. I was always told Multecs cant be cleaned but he says that isn't so. I don't know where to go from here. I'm taking it to the dealership next week. It never has thrown a trouble code.
Well I started trouble shooting and one thing led to another.
The evaporator canister charcoal pellets had filled the vacuum line and solenoid and the fuel pump and pressure regulator were an attempt to find the cause of the fuel rails not holding pressure.
Haynes manual said if its hard to start when engine is cold it is one of those things so on and on. I have found numerous errors in Haynes manual in all kinds of areas.
Then another reason for replacing all those things was pure desperation.
I have Multec injectors. I went to a fuel injector shop and he says he can pull them and clean and flow test them. I was always told Multecs cant be cleaned but he says that isn't so.
I don't know where to go from here. I'm taking it to the dealership next week. It never has thrown a trouble code.
It usually becomes that.
Not sure what you are trying to say but if you have issues with the canister, you can plug the hose going to the canister up and remove the crap and cap off the vacuum going to it.
Either get the FSM or don't bother to get a manual. It is a waste of money.
The way to fix it is to do a diagnosis and go from there and not just toss parts at it. Great for stimulating the economy and pisses you off. If you get real lucky, you might stumble on the problem before the wallet runs out.
I hope you didn't go to him because either he is an idiot or a crook. Cleaning Multecs are like having sex with your sister. Sure, you CAN do that but it isn't the best idea in the world. Multecs can be flow benched like any other injector. Problem is that it isn't worth the money. You see, once you put the solvent in the fuel, it will corrode the coils and short them out. The solvent is your gas with Ethanol. You will get ethanol in your gas so sooner or later, it will mess the coils up. Get the Bosch 24pph reman from FIC and dump the Multecs.
If you don't know what the problem is, your new name is Ben. As in Ben Dover. I would start with the reman 24pph injectors and go from there. Before you ask, you have a 91 so it does NOT have a cold start injector so you have 8 injectors instead of 9. THIS is probably what you need
Take it from someone who's been there...don't take your car to a dealer for injector problems. Chevy will charge you about $125 for each injector plus about $400 labor. Call Jon at FIC and talk to him. I bought a set of Delphi's for under $500 and wrenched it in about 4 hours. Make sure you get a 4 to 6 inch long torx driver with a 3/8 drive socket attached, it will make the job easier. One size fits all
And lastly, don't go for cheap and only replace to injectors that have a bad resistance reading, you'll just have to go back in like I did after a couple of months to change the rest.
And lastly, don't go for cheap and only replace to injectors that have a bad resistance reading, you'll just have to go back in like I did after a couple of months to change the rest.
I don't like resistance readings simply because they are abused. People look at the DVOM and think the reading is ok therefore the injector is ok. I can break the bottom off and if the coil is intact, you will get a good reading. I have bench tested them and in about 3 years, I will have a drop of 20 to 30cc of flow and you cannot feel it because it comes on so slightly.
Im sure GM is going to bend me over if I take it to the dealer but I know if it isn't done right I know who to blame. I am pretty fair at replacing or repairing almost anything until it comes to the engine or electrical. Suspension and brakes anything else Im good but fuel injection and engines not so much. I always end up with a vacuum leak or something and end up doing the job twice. I really appreciate all the input. Im still not sure why its so hard to start when it has set for a couple days but after running will start instantly all day long. Sit over night and hard to start again. Also my MPG around town is about 13 at best. I had a JET stage one chip in it and it seemed to do better on the highway at about 21 MPG but that piggyback chip always worried me. If I could get this fuel issue fixed Id be good to go other than the electrical gremlins, mainly crappy alternator that seem to plague all corvettes,
Im sure GM is going to bend me over if I take it to the dealer but I know if it isn't done right I know who to blame. I am pretty fair at replacing or repairing almost anything until it comes to the engine or electrical. Suspension and brakes anything else Im good but fuel injection and engines not so much. I always end up with a vacuum leak or something and end up doing the job twice. I really appreciate all the input. Im still not sure why its so hard to start when it has set for a couple days but after running will start instantly all day long. Sit over night and hard to start again. Also my MPG around town is about 13 at best. I had a JET stage one chip in it and it seemed to do better on the highway at about 21 MPG but that piggyback chip always worried me. If I could get this fuel issue fixed Id be good to go other than the electrical gremlins, mainly crappy alternator that seem to plague all corvettes,
Not sure what the off the shelf chips are good for except to make you think that you got performance after spending money. Hyperjunk for instance will turn on the fans earlier. Check your IAC counts and see if there is an air leak first. You never told us if you used new gaskets or not.
Well I havent been back on in a bit but to follow up. I replaced all the injectors and fuel filter, fuel pump, fuel pressure regulator and fuel sending unit plug wires and distributor cap. No change. Still hard to start. I have had four people tell me four different placed the fuel pump relay was located and still havent found it. Its not under the driver side dash. Only ZR1 has one there. Its not under the passenger kick panel. Could it be behind the glove box up high?
It hasn't ever thrown a code. I have a Autoxray Codescout 2500 and hasn't thrown any codes it has detected either. Ive replaced the whole fuel system and it still doesn't build the fuel pressure they say it is supposed to. builds about 32 psi with vacuum hooked to fuel regulator and around 40 without it hooked up. Replaced all injectors and sensors;
Not sure what the off the shelf chips are good for except to make you think that you got performance after spending money. Hyperjunk for instance will turn on the fans earlier. Check your IAC counts and see if there is an air leak first. You never told us if you used new gaskets or not.
I have replaced every part of the fuel system including injectors and fuel sending unit. Fuel pressure regulator and every other sensor on the engine and exhaust. It still doesn't build what the manual says it is supposed to. Builds about 32psi fuel pressure. Manuel says the idle speed is supposed to be 400 rpms. I cant see that being possible. I have never seen a car idle that low. It throws no codes. No check engine light. Have a autoxray code scanner and it doesn't show anything. Just hard to start first time every day after that it fires right up. start it in the morning and at 5pm fires off instantly.
Take another look at the temperature sensor on the front and connections. And did you replace the pulsater on the fuel pump with a submersible fuel line. When you key on without cranking do you hear the pump run for two seconds?
Last edited by antfarmer2; Aug 28, 2016 at 10:47 PM.
It still doesn't build what the manual says it is supposed to. Builds about 32psi fuel pressure.
Manuel says the idle speed is supposed to be 400 rpms. I cant see that being possible. I have never seen a car idle that low.
It throws no codes. No check engine light. Have a autoxray code scanner and it doesn't show anything.
Just hard to start first time every day after that it fires right up. start it in the morning and at 5pm fires off instantly.
So at key on engine off it is 32? Does it hold after you turn off the key and for roughly how long?
I don't think that is right. I suspect you should, as I always do, get a scanner to set it by IAC counts.
All that will do is say whether you have something that really is out of whack or not. You could have saved money and bought a paper clip to read codes.
If you set the IAC counts correctly and check what the ambient temp is and that should be your sensor temp and what the ECM sees. The code scanner will NOT tell you that. Also how is the timing?
So at key on engine off it is 32? Does it hold after you turn off the key and for roughly how long?
I don't think that is right. I suspect you should, as I always do, get a scanner to set it by IAC counts.
All that will do is say whether you have something that really is out of whack or not. You could have saved money and bought a paper clip to read codes.
If you set the IAC counts correctly and check what the ambient temp is and that should be your sensor temp and what the ECM sees. The code scanner will NOT tell you that. Also how is the timing?
It is at 32. It doesn't hold that long but I've replaced all the Injectors, sending unit, pump twice, pressure regulator and filter twice. Hasn't changed anything. I replaced the temp sensor on front of the manifold twice also and O2 sensor. There is nothing on the fuel system that isn't new. Chevy dealer had it for three weeks replacing the injectors and said it had a delayed start with them also but no codes. Evidently if their computer doesn't say replace this then they don't know what to do.
It is at 32. It doesn't hold that long but I've replaced all the Injectors, sending unit, pump twice, pressure regulator and filter twice. Hasn't changed anything. I replaced the temp sensor on front of the manifold twice also and O2 sensor. There is nothing on the fuel system that isn't new. Chevy dealer had it for three weeks replacing the injectors and said it had a delayed start with them also but no codes. Evidently if their computer doesn't say replace this then they don't know what to do.
What is at 32? Key on Engine off? Engine running? Engine running with hose off? You are doing a great job of tossing parts at it. We can keep doing it or you can try to do some proper diagnostics. Proper diagnostics needs proper steps. Lets start with KOEO and see if it gets to 32 or 42. If it does, we can proceed with starting it and seeing what it is. Once we get there, pull the hose off and see what it does. That is the beginning steps we have to take.
Fuel delivery problems
