Weird starting ritual. Fuel pump?
Thread Starter
Teching In
Joined: Nov 2010
Posts: 10
Likes: 0
Weird starting ritual. Fuel pump? 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.
1995 Z28 M6. Basically stock.
On The Tree
Joined: Dec 2007
Posts: 126
Likes: 1
From: Paso Robles, CA
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.
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.
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.
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.
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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.
On The Tree
Joined: Dec 2007
Posts: 126
Likes: 1
From: Paso Robles, CA
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.
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
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?
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.
TECH Regular
Joined: Jul 2006
Posts: 452
Likes: 0
From: Sacramento, CA
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.
TECH Regular
Joined: Jul 2006
Posts: 452
Likes: 0
From: Sacramento, CA
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.
TECH Regular
Joined: Jul 2006
Posts: 452
Likes: 0
From: Sacramento, CA
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.
