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the leakdown will be tell tale. post up results here.
through controlled testing of each component, you can diagnose.
when you are doing the fuel pressure leakdown test:
id.sending and return lines
clamp return line
have a helper clamp the sending line right after the key on pressurization event. this rules a leaky one way valve in the pump body allowing pressure backwards. if the return line is clamped, only way it loses pressure is perforation in lines or regulator, or injectors.
i use vice grips with black tape around teeth and a rag over the lines.[/QUOTE
VikingTrad3r-
Roger that. And if pressure was steady until I unclamped send line, that points toward leaky pump?
Sounds like we may be dealing with a 2 fold issue (injectors and/or regulator and fuel pump). I need to get some vice grips and black tape. Will post update tomorrow evening. Thanks again 👍😎
it would point to the check valve / one way valve having failed. Ive had that, car ran fine. but when power turned off, system de pressured quickly.
so back flow through the pump doesn’t necessarily indicate the reason for your issues. if sock was plugged or pump weak, that could be cause.
it would point to the check valve / one way valve having failed. Ive had that, car ran fine. but when power turned off, system de pressured quickly.
so back flow through the pump doesn’t necessarily indicate the reason for your issues. if sock was plugged or pump weak, that could be cause.
leak test is mostly for id’i g leaky injectors.
OK gents….
Here’s the latest developments with the little red rescue ‘Vette. Sorry for the long post. A fellow forum member came by Fri and Sat to give me a hand.
Friday- Replaced fuel strainer sock. Old one was dirty but not horrible. No sign of rust. Replaced fuel pump with used unit from the forum member. Was told pump was working fine but replaced to meet higher needs created by multiple engine upgrades he’d done.
Hooked up fuel pressure gauge. Clamped off fuel return line, pressurized fuel rail, and immediately clamped fuel send line. Fuel pressure jumped to 90 psi. Within two min it dropped to 76, within five min dropped to 71, within 10 min dropped to 65, within 15 min dropped to 62psi. Unclamped the return line. Pressure stayed about 61 psi for the next three or four minutes.
Was concerned pressure had jumped so high initially so I released pressure from the gauge and retested by re-pressurizing the rail and clamping both send and return lines immediately after rail had pressurized. Pressure started at 37 psi, drop to 34 within five min, and 32 psi within 10 min. Then I unclamped the return line. Pressure stayed at 32 psi. I waited for five minutes then unclamped the send line. Pressure dropped steadily to 16 psi.
What??
Sat- Our fellow forum member brought over his ALDL scanner. Strangely, when we hook the scanner up my idle RPMs would increase and slowly creep upward to almost twice the norm. I’m still learning about information that’s provided by the scanner but 3 things stuck out for me. BLMs were pegged at 160. Throttle position voltage looked pretty good at .568. And O2 milliVolt reading was bouncing between low 400s to low 500s then for a split second dropped down around 31. I’ve tried attaching a small video of the live scanner taken from my phone but not sure if it uploaded.
our fellow forum member also gave me a new FPR that he was not going to use because he had switched to an adjustable one. So I’ll be putting that in.
Based on comments from another forum member I purchased an IR Heat temp checker. Was advised cats should show higher temps at outlet than inlet. If temps lower at outlet then inlet cats could be clogged. Main cat showing 40 degrees cooler at outlet than at inlet.
I need to correct something I stated earlier in my posts. The car is actually stumbling when you try to accelerate at 1900 RPM, not 2900.
Very interested to get feedback on what my next steps should be.
Thanks very much 🙏🏼
Last edited by JstAskin; Feb 20, 2022 at 03:29 PM.
Reason: Additional information
Well, ran into a little delay in the process. Was taking off Plenum, runners etc. to do some cleaning and replace the fuel pressure regulator. Apparently previous owner thought it necessary to tighten down runner to plenum bolts extremely tight. Got everything taken loose on driver side and loosened up one on the passenger side. Went to do the lower bolt going from runners to plenum and ended up stripping the head out just a bit. What’s the best way to get that bolt out without damaging anything else?
Based on comments from another forum member I purchased an IR Heat temp checker. Was advised cats should show higher temps at outlet than inlet. If temps lower at outlet then inlet cats could be clogged. Main cat showing 40 degrees cooler at outlet than at inlet.
When checking the cat temps, you must drive for a while or put some load on the engine to get to full temp and plenty exhaust. At idle, there is not enough in the exhaust to get the cats doing enough to get the temps up.
Also, have to check the cats right after drive, they will cool quickly.
The center cat may be cool if the precats do all the work already. Pretty sure this is correct, I may be misremembering.
My experience is that allowing a car to idle until coolant temperature comes up will fire off the cats. Learned this trick from an exhaust shop and have used it on my own cars. If you can drive it under load, that's better. But it's not required.
Regardless, a cat that's not clogged will either show a temperature rise if it's fired off or a small drop if it's not fired off but otherwise open. Assuming you've let things run long enough to come up to temperature, 40F at idle indicates a significant restriction.
When checking the cat temps, you must drive for a while or put some load on the engine to get to full temp and plenty exhaust. At idle, there is not enough in the exhaust to get the cats doing enough to get the temps up.
Also, have to check the cats right after drive, they will cool quickly.
The center cat may be cool if the precats do all the work already. Pretty sure this is correct, I may be misremembering.
kael (cool name. Sounds like your from Krypton)😎 Thanks for the feedback. I’ll try to check temps again right after driving. It’s been a while since I’ve been under the car but I think the previous owner deleted the pre-cats.
My experience is that allowing a car to idle until coolant temperature comes up will fire off the cats. Learned this trick from an exhaust shop and have used it on my own cars. If you can drive it under load, that's better. But it's not required.
Regardless, a cat that's not clogged will either show a temperature rise if it's fired off or a small drop if it's not fired off but otherwise open. Assuming you've let things run long enough to come up to temperature, 40F at idle indicates a significant restriction.
hornetball-
she had been driven and was warm enough for coolant to be in the 220+ range. Another tidbit. Out of curiosity I did a temp check on the exhaust outlets. Both mufflers have dual outlets. Temps for both outlets on driver side muffler were very close to the same. But on the passenger side muffler one outlet had temps about the same as the driver side but the other outlet was considerably cooler. I held my hand up behind both passenger side outlets and the cooler outlet had noticeably less exhaust flow. Is it possible that material from the main cat could have came back and clogged part of the passenger side muffler as well? Thanks for sharing your insight. 🙏🏼
YES!! Was able to get stubborn Plenum bolt out. Have Plenum and runners removed. YUCK!… 😳 There is a ton of buildup inside the Plenum. Would like to clean build up from inside of Plenum, intake runners, and throttle body as much as possible. What product has worked well for you guys?
what i did was soak my plenum and runners (and intake) in gas, in a tupperware bin. it worked well, dissolved the carbon. safety first!
carb cleaner works well for thw carbon too. berryman chem dip same thing.
for the aluminum exterior, the best thing is eagle 1 etching cleaner, or, if u r in canada, its called alumabright off amazon or aqualum from napa. you spray that stuff on, and rinse it off. for severly discoloured aluminum parts (i did an 86 once where the intake manifold base was crazy scaled up and pitted. this stuff made it look new) you may need to agitate it and apply a few coats.
what i did was soak my plenum and runners (and intake) in gas, in a tupperware bin. it worked well, dissolved the carbon. safety first!
carb cleaner works well for thw carbon too. berryman chem dip same thing.
for the aluminum exterior, the best thing is eagle 1 etching cleaner, or, if u r in canada, its called alumabright off amazon or aqualum from napa. you spray that stuff on, and rinse it off. for severly discoloured aluminum parts (i did an 86 once where the intake manifold base was crazy scaled up and pitted. this stuff made it look new) you may need to agitate it and apply a few coats.
VikingTrad3r-
Once again, great advice 👍 I should probably remove the sensor on the bottom of the plenum? Thinking I will also remove valve covers for cleaning, repainting.
Thanks for responding. I’d rather get direction from savvy forum members than from YouTube…..😳 Cheers 🍺
there are a few threads about restoring the vc’s. As long as you dont fret about the horrible casting from factory, they can be made quite pretty!
a major disagreement was the need to heat the vc’s after cleaning, to help oil and volitiles out of the porosity before paint. For my results, its been a must, on the bbq, with tin foil underneath. others, Joec i think?, he had great success without doing that step. 👍
Is it possible that material from the main cat could have came back and clogged part of the passenger side muffler as well? Thanks for sharing your insight. 🙏🏼
It's more likely that your passenger side muffler has failed. Might be time to visit an exhaust shop.
It's more likely that your passenger side muffler has failed. Might be time to visit an exhaust shop.
hornetball- Probably true. Now to find a reputable shop here in Vancouver WA/Portland OR area. Luckily I’ve made a connection with a fellow forum member that lives in the area. I’ll see if he has a good recommendation👍.
there are a few threads about restoring the vc’s. As long as you dont fret about the horrible casting from factory, they can be made quite pretty!
a major disagreement was the need to heat the vc’s after cleaning, to help oil and volitiles out of the porosity before paint. For my results, its been a must, on the bbq, with tin foil underneath. others, Joec i think?, he had great success without doing that step. 👍
VikingTrad3r-
Just looking for a decent result. Current VCs badly discolored w/ flaking. Possibly prior owner tried repainting? Does heating them as part of prep help prevent that? Certainly don’t want to go to the trouble of repainting only to have it look like crap a relatively short time later.
Keep that wisdom coming brother 😎
Ok gentlemen,
I have Plenum, runners, and fuel rail removed. Parts ordered and in contact with FIC about replacement injectors and seals to rebuild the fuel rail. I have a question about the warm up injector. Should it be sitting snugly into a opening in the intake like fuel rail injectors? Mine appears to be held in place by a plate that is secured by one of the bolts going through the base of one of the intake runners. The warm up injector is not snug where it enters the intake like the injectors on the fuel rails. Is this correct? I tried to upload a couple of pictures to illustrate. Let me know if this is a standard set up or needs correction. Thanks very much for your guidance. 🙏🏼 Where the warm up injector goes through the flange at the base of one of the intake runners. On the left, the bottom of the injector and the plate that secures it. On the right is the hole in the intake where the injector goes into the intake. It’s not held snug by an O-ring like injectors on the fuel rail. What prevents air or fuel leaks?
If you go to home depot and buy Muriatic Acid and mix it 50/50 with water You can make a pretty good Aluminum Cleaner. And its cheap enough you can make up a batch and soak parts in it. Try it on a small part and test first. If its high quality Aluminum it will brighten it right up. If its some sort of pot metal it will dull it right up. On a late C4 the AC lines will look like new again. The ECM will turn black.
Ok gentlemen,
I have Plenum, runners, and fuel rail removed. Parts ordered and in contact with FIC about replacement injectors and seals to rebuild the fuel rail. I have a question about the warm up injector. Should it be sitting snugly into a opening in the intake like fuel rail injectors? Mine appears to be held in place by a plate that is secured by one of the bolts going through the base of one of the intake runners. The warm up injector is not snug where it enters the intake like the injectors on the fuel rails. Is this correct? I tried to upload a couple of pictures to illustrate. Let me know if this is a standard set up or needs correction. Thanks very much for your guidance. 🙏🏼 Where the warm up injector goes through the flange at the base of one of the intake runners. On the left, the bottom of the injector and the plate that secures it. On the right is the hole in the intake where the injector goes into the intake. It’s not held snug by an O-ring like injectors on the fuel rail. What prevents air or fuel leaks?
if my memory is right, there is supposed to be an oring on the coldstart injector. yes it would be a vac leak (causing high idle, possibly worse) without.
If you go to home depot and buy Muriatic Acid and mix it 50/50 with water You can make a pretty good Aluminum Cleaner. And its cheap enough you can make up a batch and soak parts in it. Try it on a small part and test first. If its high quality Aluminum it will brighten it right up. If its some sort of pot metal it will dull it right up. On a late C4 the AC lines will look like new again. The ECM will turn black.
as far as i can recall, pot metal parts: thermostat housing, all accessories and their mounting brackets. i dont touch the accessories with any even heavily diluted acid as im not sure it would be good inside the part. for brackets and tstat neck, i have used a very weakened acid and it allows it to come clean, but if left to dwell on part, it seriously dissolves the part. mottles and dulls it.
muriatic is waaaaaaaay stronger that the retail products above. it will work. id suggest after cleaning u will want to dip the parts in a base, baking soda water, to stop the reaction.
if my memory is right, there is supposed to be an oring on the coldstart injector. yes it would be a vac leak (causing high idle, possibly worse) without.
VikingTrad3r-
I read through the valve cover info on the link you provided. Wow!! 😳
not sure if I’m less confused or more confused after reading The different posts there. But I’ll figure it out.
As for the aluminum brightener, I went to Napa. They have some good stuff that works well and doesn’t require mixing, etc. Tomorrow I’m going to Block off injector and intake ports to prep for cleaning the top of the intake manifold and front of engine while I have lots of access. Can you recommend a safe effective cleaner for this task? I’ll be letting the runners and Plenum soak to remove carbon deposits while I’m cleaning the engine.
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