I had a custom dynoflash last year and never had a single problem car ran great, recently however I have had a very odd starting problem. If I let the car sit in the high heat (90 degree day) it struggles like hell to start and the A/F ratio stays super lean (17 to 1) after a few minutes and some reving it all goes back to normal. Any ideas? Also after my second round of custom dynoflash I started getting the p300. Just wondering if you had any insight as to whats going on.

 

What are your mods ?

 

I have 264/272 cams,HKS RS intake, stock 04 9.8 turbo, helix IC pipes,SMC trunk mounted alky kit (100% meth) BR 3" turbo back with test pipe, walbro fuel pump Nisei engineering IC, 1G BOV and a custom dynoflash. I also have a Perrin fuel rail with stock regulator, just so i could have a spot to place my fuel pressure sensor.
I am going to swap out plugs, check for boost leaks and check to see for exhaust leaks in the AM 1 more time in case I missed anything. Its odd that I also noticed I lose all my fuel pressure within 2 hours of letting the car sit.

* let me just add I dont think its the tune Im just really at a loss for what it could be

 

Maybe your fuel pump is going bad? walbro?
A friend had similar issues to yours and replaced his year old walbro. Worked fine after that.

 

Evotech That is possible maybe Ill swap the stock pump back in and see what happens, it is a walbro

 

I agree it sounds like a fuel pump that is going bad

I would swap in a new walbro unit

 

Remember - the flash parameters are permenently fixed

If its something that suddenly goes wrong after working well - its ALWAYS mechanical - meaning engine mechanical - electrical or boost etc

Best of luck

 

Could be normal.

High heat = evaporated fuel in the line.
This causes an air pocket in the fuel lines and it will struggle to start until the air clears out and fuel starts to flow to the injectors.
.

 

Well not "normal" I have been in AZ, NV and TX in well over 100 degree temps and never seen any vapor lock in any one of dozens of evos I have tuned in hot conditions


Keep in mind - the fuel filter on evos is in the fuel pump housing - I am sure that was the cars get more miles we may also see some of them get cloged

I am suggesting that this owner try a fresh walbro just to be safe

 

if he has ethenol in the fuel where he is, that could be part of the problem. In the chicagoland area and others that have up to 10% ethanol mandated by law, Mercedes has seen rare issues with the twin turbo 12 cyls basicly vaporlocking after heatsoaking for a while. we are installing updated fuel pumps and fuel pressure regulators that hold higher rail pressure at shutdown to combat this new issue. Possible that others may be experiancing the same issue?

definatly try the pump though and let us know if the pump resolves the issue.

ps I beleive these new laws took effect within the past year

 

Ah - ethanol is an unknown factor !!!!!!!!!! Good point !

 

I've had my stock Evo vapor lock after sitting a little while after hot shutdown. This occurred when I tried to start after a stop at a rest area along the interstate last summer.

The system on the Evo is not different than what was used on the DSMs (pressure regulator vented to atomphere) and they sometimes had hot start problems. So, anyway, I hate to see you chasing something that may be 'normal'.

 

yeah leaky fpr will cause a hard start but it will be at cold start also not just high heat start situations

 

90 degree weather is absolutely no harm for your car. Most of cars in AZ are sitting at 115 degrees with temp inside the engine bay of 200 plus degrees(after driving it) and I haven't heard problems of temp problems starting a car .


That is a typical problem of carburated power cars though. It also sounds to me like the fuel pump might be malfuntioning..

I decided to respond to this topic because since you mentioned that you were Dynoflash, SMC trunk mounted, hot weather and similar mods a thought I follow under that same criteria except 25 degrees hotter.

One thing I must say is that the alcohol methanol from the trunk tank evaporates significantly..

Carlos

 

We have switched over to ethanol blend and now that you mention it, this is when this problem did start. Last summer when I was tunned by Al at Pruven it was hot as well and never a problem. I swapped in the stock pump last night and turned the boost down to stock. The driveability problems have gone away but the first thing in the AM problem persists. Please note I am not blaming the TUNE, I am asking Al simply because he is my tunner.

Of course my only problem with blaming the ethanol is this, my buddy with an 04 RS fills up at the same gas station does not share in this problem.