hbnavea

Whenever I start my car I have to turn the key to start and let it prime for about 5 seconds, click it off then click it back to start and re-prime for 3-5 seconds then immediately crank it. It will start normally and idle normally, if i do this process. BUT if i go to start it right away it will crank for awhile (longer than normal) then start and hold high RPM for about a minute or so then drop back down to normal idle. What could be the cause? FP regulator? Fuel pump? Spark plugs? Once its driving it runs like a champ.

1995 Z28 M6. Basically stock.

RamAir95TA

iTrader: (2)

Do a fuel pressure test for a more definitive diagnosis. A gauge is a great investment, and most parts stores carry them for around $35.

Formula Freak

I am experiencing the exact same symptoms on my car, although I only get the high idle once in a while on a hot start. It clears up and idles normally after about 15 seconds in my case.

I haven't troubleshooted it with a gauge, but I've read on here that the most likely cause is a faulty check valve in the fuel pump responsible for a holding a prime over extended periods. When the check valve is broken, fuel pressure goes down fast after the car sits for about 20 minutes, causing the extended cranking condition or the need to cycle the ignition a couple times, to build up adequate fuel pressure.

I've been driving my car like this for almost a year, with no drivability issues once running. Not gonna mess with it until the fuel pump dies.

hbnavea

Yeah exactly how I feel. But a new walbro 255 fuel pump would fix this problem? I might go ahead and fix it when I find a cheap one.. If this would even fix it.

Tbird232ci

iTrader: (4)

I had the exact same symptoms. Would take 2-8 attempts to start the car in the morning. I ended up getting system lean codes, and as the condition worsened, it wouldn't run for anything in the upper RPM's. I put a Racetronix pump setup in the car, and the issues were cleared up.

Even though it worked out for me, I would still say to get a fuel pressure gauge. I put new O2's in the car, so I know they didn't cause the lean codes, I had no vac leaks, or anything of the sort, and my injectors were recently cleaned, so everything pointed to the pump for me.

hbnavea

I guess a walbro 255 is on my to do list.. Jw does it make a louder noise when priming than stock? I always liked that noise haha

RamAir95TA

iTrader: (2)

If you want a louder pump, remove the matting in the trunk.

But before you go replacing the pump, get the gauge.

flippincamaro

iTrader: (23)

We put a 255lph walbro in my dads 2000 silverado, An the check valve is bad we have to cycle the key 2 to 3 times then crank for it to start up.

food nd cars

ordered the pump from thunderracing and will be doing the trap door method. I will update if this fixes the problem

transamws6_97

iTrader: (5)

yup I have the same problem and I got a fuel pressure gauge and checked it and sure enough when i put the key to start the pressure would go up to normal then quickly shoot back down to 0 so the check valve is def bad...and the sad part is the fuel pump is only like 2 yrs old.

Formula Freak

For the record, my car still has this condition and I just made a 300 mile round trip. The car did great. So I don't think a bad check valve is something that can leave you stranded. Just a minor nuisance to me when crankin' it up.

transamws6_97

iTrader: (5)

ya my car has had this problem for over a year and ive made numerous trips home and back from school which are about 300 miles with no issues...just a pita actually thinkin about getting racetronix system instead of bilsteins w/ my tax return money

joelster

Replace the fuel filter since it is a regular maintanance item. You may have 1 bad injector that is bleeding down pressure after a shutoff.

transamws6_97

iTrader: (5)

you can check that by unbolting the fuel rail and lifting up the injectors and see if any leaks when you pressurize the system correct? If its bad it will leak gas right?

fex77k

iTrader: (2)

Do you run a aftermarket FPR? Not saying it is your problem, but they don't hold any pressure after the pump is shut off.

transamws6_97

iTrader: (5)

no it is stock fpr

food nd cars

i already replaced my fuel filter. Reason for going for a new fuel pump is that it has developed a slight miss in the higher rpm's (maybe miss is the wrong word, more like a slight lack of power) and I am installing a wideband gauge to start tuning. I just want to make sure my fuel delivery is 100% before I start tuning it and its annoying as **** when i'm in a hurry and i have to cycle the key 2-3 times just to start it. Also Thunderracing has $5 off and shipping is around $12 so all together it was about $152 shipped, which i think i well worth fixing the faulty check valve.

joelster

A wideband won't tell you if you need a new fuel pump. A wideband will tell you your a/f ratio. A fuel pressure guage will tell you what you need to know.

food nd cars

i know that.. I'm saying that before i start the tuning process i want to make sure that my fuel problem will not be an issue.. the wideband is for the tuning.

btw. all Walbro 255 lph racetronix are on back order at thunderracing and at racetronix and as of right now WS6store is the only place that has em.. for LT1's. They have like 3 left.

food nd cars

Here are a few pics of the install. only problem i had was separating the stock bucket and making sure the walbro fit snug inside the bucket. The problem was fixed and the whole install took about an hour and a half.