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Discussion Starter #1
I have a MK1.22 that I race in the chump car series and im having a problem with it bogging. Once the car warms up for just about 20min it will start bogging after 4K RPM. As time progresses it will start bogging at 3K and get worse from there. It starts as no power above that RPM then its like someone killed the ignition if you try to go over that RPM. I have tons of spare parts so I have started trying to diagnose the issue by swapping parts. So I have swapped the following with no change.
Distributor
Ignitor
coil
Fuel Pressure VSV
Fuel pump
ECU
water temp sensor
MAP
I have also checked/ replaced all vac lines

So at my wits end I tried to pull the codes off of the ECU and to my surprise I got code 24,43.
So now Im trying to figure out where my IAT is and code 43 im at a loss on.
Do you guys have any recommendations on what to do next?
 

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Discussion Starter #4
I think so, I replaced my FPR which had no change. So even though I replaced the pump and I was getting full power to the wiring right above the pump, I decided to get a fuel pressure gauge. Once I installed it I could see my fuel pressure drop significantly. So I'm thinking it has to do with the wiring to the pump inside my tank. Right now I have the tank out working on that but realized my tank has tons of rust in it. So I plan to take it to get cleaned today. I will report back once I get it all back together.
 

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I'm willing to bet the rust is causing all your problems. Most likely clogged the fuel pump and filter, reducing the fuel pressure. I'd change the filter sock before putting everything back in. You should replace your fuel filter also.
 

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Discussion Starter #6
Well I would agree with you on the rust except for when I was at Road America I had to finish early because of low power. So I pulled off and changed the pump in the parking lot. I went back out and had the same issue. So then you would think possibly an clogged fuel filter which I replaced before Road America. I just (as of 15min ago) finished installing a Walbro and doing new wiring and relay on its own circuit, I reused the fuel filter. She no longer drops pressure and runs like a top. So Im going to say that the rust was no good but was not my problem, it was bad wiring inside the tank.
 

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Discussion Starter #7
Ok, I spoke too soon, I went out this weekend on a spirited drive and it started doing the same thing again. I pulled over at an auto parts store to replace the fuel filter thinking that the fuel filter is the last thing that could be causing it. When I pulled it off you could tell that it had tons of rust in it so I was for sure I had the culprit. As soon as I took off it started acting up again. So right now Im at a loss, I have my fuel pressure sensor right between the fuel filter and fuel rail about 3 inches away from the fuel filter. When it starts acting up fuel pressure drops when I give it gas. One thing I also noticed is that when I first start the car I can pinch the return line and watch the fuel pressure rise. once it starts acting up I can pull over and the gauge will be at 40PSI off throttle but when i pinch the return line it feels like no pressure is in there and the gauge shows no change. At this point I think I have to have a clogged fuel line between the sensor and the fuel pump. So I am going to pull the tank again and replace all the fuel lines with new rubber, even the hard lines. I don't know what else it could be.
 

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Discussion Starter #8
So last night I just wanted to try to test some things so I took the Fuel filter, rail and all hoses after the fuel tank hard lines out of the equation. So I took a new rubber fuel line and went from the hard fuel feed line at the back of the tank by the fire wall and hooked my fuel pressure sending unit to it and then went back into the return. So I could see how consistent my fuel pump was putting out pressure. So then i jumped the fuel pump directly to a 12v source to rule out wiring even though I have the wiring totally separate now. The pump runs at an unrestricted 10psi which is about normal but after about 10 min pressure begins to drop to 0. If I unhook the power wire to the pump and immediately plug it back in (seriously like 1 sec) it starts the timer over again meaning I have about 10 min of run time before pressure starts to drop. WTF. At this point I would say I have a bad pump but this is my 3rd pump that is doing this. So has anyone had problems with the junction right above the fuel pump where the power wire from the car plugs into the top of the tank and then picks back up inside the tank? (i dont know what that is called).
 
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