Good morning, I have a 1993 Honda del sol si. Swapped b16 turbo motor running on Hondata s300. The problem I’m experiencing is in the morning the car starts fine runs good. It sits outside all day in the sun and when I go to start it, it takes a second and then it starts. The start is rough, but it starts every time. I drive about 45 mins home and as I’m coming off the accelerator, it starts popping and dropping rpm very low and then has a rough idle. When I pull in my driveway, I can hear what almost sounds like whining/ air leak. The noise I’m hearing is my fuel pump walboro 255. It’s screaming. So I shut the car off let it sit, turn my ignition on and the fuel pump engages but it’s almost deafeningly loud. If I let the car sit in the garage for awhile/overnight all is good. I read a lot about main relays causing a similar issue, except everything I read was a no start condition, and no one had a walboro 255 either. This only happens when it’s above 70 outside. Please advise on any assistance on the matter. Thank you.

 

Bump

 

I would almost think there's a problem with the pre-filter on the pump getting sucked into itself causing it to try really hard or just something odd going on with it. I've had my walbro 255 running strong for 18years so I would say they are reliable. Mine only does the short whine priming then all is good.
I've read about others with similar problem as yours but was only fixed when they changed out the pump. So, that's why I would think possibly something attached to the pump is starving it since it does still work right?
I would drop the tank and pull the pump and inspect. Only takes about 1/2hr to drop the tank.

 

Yea the only thing with that is, it’s only when it’s hot outside. If it’s cool I can drive all day 8 hours continuously and not have an issue at all with the car or have any noise at all with the pump. I have another walbro 255 coming I’m gonna install, I’m just trying to get some insight on the main relay problem many are talking about, saying they only have a problem when it’s hot outside.

 

That is strange with the main relay, have you opened yours to check the condition of its internal connections and circuit board for possibly something shorting or odd looking?
If you can get another one to borrow or cheap from a wrecker, wouldn't hurt to swap yours out to see if it's the relay or not before going into the tank.

 

Yea it definitely is strange and blowing my mind up. I haven’t messed with the main relay yet, I have one on order from Honda. I have read a lot about main relay problems in the heat, that the solder expands and causes the connection to break. But every single one was a no start condition, mine starts every single time, just more difficult when the car has been sitting in the sun all day. Even when it’s hot in my garage it will start with no issues, only when sitting outside in the heat, above 70 will this happen.

 

This is the main relay out of the car.

 

The 3 joints on the top left look a bit dark.. and it trails onto a band (trace wire or whatever its called)..
The center top double pin almost looks like it has a crack formed on the very top going around the solder. Hard to say though..
Might be worth just replacing it.

 

So update, replaced the main relay, replaced the walbro 255, replaced the fuel filter and orings, installed fuel pressure gauge at the fuel filter, when key on engine off the gauge reads 40 psi, when running during the problem when fuel pump is screaming, the gauge is fluctuating between 20 and 40. But after all this the problem is still there only when it’s hot and sitting in the sun, and running for about 45 mins to an hour.

 

Your problem has me interested as I have the same pump and just incase for future reference I would like to know the fix to this. One thing I read was people mentioning the gas cap. Maybe if yours is stuck closed and not relieving excessive built up pressure from when it gets hot, possibly it's affecting the fuel system operation and disturbing your pump causing the noise.
Maybe next time it happens, shut the car off and remove the gas cap then restart it??? Cross your fingers it's the stupidest fix.

 

I have already done that, I release the pressure in the tank and the idle changes, but the pump does not. I’m starting to think when it’s hot I’m losing power or ground to the pump. I’ve read a few things about adding a plug and play relayed harness to it. But I haven’t ordered this yet. But I’m looking.