Low power, slow to get in plane. Intermittent backfire

Rick2752 · **Posted:** Wed Jul 30, 2014 9:32 am

2001 vista 248 5.7 gsi low power getting up on plane. Sometimes when it's under load it will cough almost backfire. It happened once about 2 wks ago then a lot this weekend right after I fueled up at the marina. I changed the fuel filter no change, I am gonna look at the anti siphon valve. Haven't pulled it yet but I am leaning towards the distributor cap being cracked. My plan if attack is cap, rotor and wires, plugs and then the anti siphon. I do have a whine noise in the fuel pump but it is really only when I turn key on and it primes the pump. Anyone else have any ideas

rpengr · **Posted:** Wed Jul 30, 2014 12:18 pm

Timing comes to mind, but there is not much reason your timing would have changed.

Other than that your plan of attack sounds pretty good. As Lou has said, you could save your money on the plug wires if you just check their resistance to see if they are good. And then add Check Fuel Pressure to your list? And check for codes?

Rick2752 · **Posted:** Wed Jul 30, 2014 12:59 pm

Is there a way to see if there is a code stored? I have an obd II reader but I'm sure it won't work. Any secret methods to see what codes are? Are the codes saved after battery is turned off ?

rpengr · **Posted:** Wed Jul 30, 2014 2:33 pm

I have a carbureted engine, so I will have to leave that for someone else to answer.

LVChris · **Posted:** Wed Jul 30, 2014 3:14 pm

I had a similar problem it turned out to be the fuel pump.
http://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=10192

LouC · **Posted:** Wed Jul 30, 2014 3:37 pm

There is a scanner that reads codes for marine systems but its pricey. The fuel pump problem is common on Volvos but you don't want to guess as they are pricey too.
As a general thing its always better to go through the ignition system first, to rule all those causes out. Once you know its not that it gets easier to narrow it down. You did say it happened right after you got gas though, right???? Anything unusual in the fuel filter?

Rick2752 · **Posted:** Wed Jul 30, 2014 7:05 pm

Not that I saw Lou. I dumped as much as possible into a water bottle to see if I had water and didnt really see any. I looked up the volvo scanners, Don't think I want to buy one of those. There needs to be an easy way to at least see if it has a code stored. I really don't want to buy a fuel pump after doing manifolds this year....lol

Rick2752 · **Posted:** Wed Jul 30, 2014 7:13 pm

Lou you talked about checking Ohms on the plug wires, Wouldn't they all vary based on their length? Are you just saying if one is literally broken it will show open. Thanks, I will keep everyone informed on my progress which may be slow, I'm working 12s at work and its best to let my boat frustration pass.

Rick

LouC · **Posted:** Wed Jul 30, 2014 7:24 pm

Yes in general that's true, but you can find differences in resistance that can affect performance. We had this happen on my wife's Toyota Camry years ago. It sounded like it was running on 2 cylinders. When I checked the plug wire resistance 2 were way high, not infinite but high. My OMC manual says that the resistance must not exceed 10,000 ohms per foot. Take a really bright LED flashlight and look at the cap and rotor for cracks and carbon tracks. Look at the plugs and see if any look fouled....
If I recall that Rinda scanner is like 400 bucks...

ric · **Posted:** Wed Jul 30, 2014 7:53 pm

Timing. Verify at least 10* BDC with a light. The dizzy can slip after time.

jgreve75 · **Posted:** Thu Jul 31, 2014 4:04 am

If your anti-siphon valve is clogged or otherwise restricting your fuel flow, you could definitely be getting a "lean pop" while your engine is under a hard load and starving for fuel. Those valves are pretty cheap to replace and free to inspect. Maybe you will get lucky and find a smoking gun there in the form of debris stirred up by your recent fill up or a sticky ball. If not, then you could move on to checking fuel pressure and making sure your ignition system components are ok.

Bliss36 · **Posted:** Thu Jul 31, 2014 7:04 am

If you're looking for a good code reader I've been using this for a couple of years now and I'm pretty impressed with what it does for the price. It not only gives codes but also live data which can really help finding issues.
http://mefiburn.com/mefiscan.asp

Also forgot to mention they have good tech support which I used to set mine up on a netbook.

Rick2752 · **Posted:** Sun Aug 24, 2014 6:11 pm

Ok so I changed the anti siphon valve, new fuel pickup tube, and new large fuel filter. All looked good. Took the distributor cap off and thought i found my problem there was a lot of salt on the bottom plate and the contacts were all corroded I can't believe it even ran. Took it out and it ran horrible, consistently backfires or misses like a cough cuts out. I haven't put a pressure gauge on the fuel pump yet but I put my hand on it while it was running and it didn't feel warm at all. I'm gonna ohm the plug wires soon.

298VISTA2000 · **Posted:** Sun Aug 24, 2014 7:21 pm

Fuel pump poisoning by ethanol.

Rick2752 · **Posted:** Sun Aug 24, 2014 7:40 pm

Actually it's the other way around. I don't really have marinas close by so have always run 89 ethanol with marine stabil. Never had an issue. I filled up at lake Norris on the water with 93 leaded fuel and it hasn't run right since. I'm down to a 1/4 tank probably gonna pump the rest of it out also and see what happens. I don't want to guess at the 700 dollar fuel pump.

www.iFourWinns.com

Low power, slow to get in plane. Intermittent backfire

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