Weird fueling issue, pump whines, car bogs when hot......

[Grabbit]

So last summer I had an issue with the way my car would run ONLY if it got hot while sitting in stop and go traffic. I would start to hear the pump whine and if I tried to accelerate moderately it would bog hardcore. So I avoided those situations as much as possible and started troubleshooting the problem. Last fall I replaced the fuel pump with a Bosch unit, replaced the filter, injectors, FPR and fuel rail (was bent for some reason). I thought the issue was gone but it just started happening again. I'm getting the same whine, mostly when stopped and idling. If I punch it will fall on its face until I get to a moderate speed and get some airflow under the car. It almost seems like the pump is overheating or not getting enough voltage or something. Maybe its the transfer pump, or evap related. I'm stumped.

Some background info: the car is a Mk2 digi II car with an OBDII swap and I kept the factory digi II pump and fuel box.

[Scotty_2.0]

Time to get a Mk3 tank. Aside from that, maybe see if you can check the voltage at the fuel pump connector. Sounds like some kind of restriction possibly.

[Grabbit]

Time to get a Mk3 tank.

Negative Ghostrider. Going to that length isn't necessary.....

[Scotty_2.0]

Lol... yes not necessary, but the better route IMO. I might suggest a fuel delivery test as outlined in the Bentley manual - assuming the voltage supply to the pump checks out. This will tell you if the pump is delivering sufficient volume.

[Grabbit]

I've rented a fuel pressure tester and everything checks out. Its going to be hard to replicate the issue for testing since it only happens intermittently. If anything I would upgrade to a MKII CIS pump.

[dogyouare]

ur fuel pump is over heating! it eventually shuts down. time to get a new one! happened with my
91 jetta
90 jetta
90 golf
86 golf
87 golf

need i say more?

[Grabbit]

ur fuel pump is over heating! it eventually shuts down. time to get a new one!

pump is new boss, also this never happened when i lived in AZ in 110+ temps....

[kpn3nc]

do you run the car close to Empty alot? check the resistance in the wires. I've had that problem before, and eventually my car died, and my relay panel was hot and I looked under there and wires were melted. I'm assuming it was because my pump would get hot/work harder, build up resistance in the lines and eventually they overheated the insulation and it was a nightmare GL

[Grabbit]

heard the pump whining yesterday but it didn't bog down, gas tank was full......

[dogyouare]

people use the 16v fuel pump for the flow. the 8v pump are weak.

but ask covered replace to mk3 tank. but if u want to keep mk2 switch pump to 16v or get aftermarket inline fuel pump

[Grabbit]

people use the 16v fuel pump for the flow. the 8v pump are weak.

but ask covered replace to mk3 tank. but if u want to keep mk2 switch pump to 16v or get aftermarket inline fuel pump

8v pump puts out plenty of pressure and volume for a NA VR swap. I know the CIS pump puts out more pressure but try and find a replacement fuel box for the different sizes of pumps. I had a brand new pump and I sold it because I couldn't find a good fuel box/housing for it....