can't rev over 2300 rpms
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=38641
Printed Date: October-07-2024 at 12:26pm
Topic: can't rev over 2300 rpms
Posted By: jtryon
Subject: can't rev over 2300 rpms
Date Posted: May-16-2016 at 1:27pm
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i had my carb rebuilt this spring, and changed out the plugs, wires, cap/rotor and points as well. i'm having a problem with the boat not wanting to rev over 2300 or so rpms now, and have looked at the firing order which is correct, and every picture of the cap orientation that i can find online. i'm still at a loss after 5 hours working on it yesterday. when i did the plug wires i did them one at a time to make sure i didn't cross one, but now i'm wondering if i started in the wrong dist cap location to begin with, or something else stupid. for reference, the boat starts great and idles great. dwell is 31, timing at 10, and advance around 580. when i rev the engine the timing goes to about 20. all that is what i have found online to be ideal for these motors. battery voltage is 12.7 with the engine off and 13.1 while running, so i know i'm getting a charge. i'm only getting 4.5 volts at the coil with the engine off and 3.5 while running, so i started tracing back the wiring to see where the voltage loss is. 12.6 volts at the ignition switch in the off position, 11.7 in the on position. 13.2 volts at the ballast resistor hot side, a little under 5 volts on the pink side. all that being said, here's my question: i have a screw-down cap, not a clip-down cap ('88 sunsport, 351w). when i look at my dist cap from the top, the front screw has the 6 and 2 plug wires on either side of it, and the rear screw has the 8 and 1 wires on either side of it. can anyone confirm that this is the correct orientation for those wires? i'm starting to wonder if they are off by one wire or something. |
Replies:
Posted By: TRBenj
Date Posted: May-16-2016 at 1:36pm
Please explain this in greater detail. Also double, triple and quadruple check your firing order. Also tell us what firing order you are using. |
timing at 10, and advance around 580. when i rev the engine the timing goes to about 20.Posted By: jtryon
Date Posted: May-16-2016 at 1:42pm
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well, those were the readings off my fancy timing gun. timing is reading at 10 degrees btdc, and when bringing up the rpms it reads at around 20. "advance" is what the gun was showing on another screen which i was just including for reference. firing order is 1-3-7-2-6-5-4-8. i have triple-checked it and i know the order is correct, but haven't brought the #1 cylinder to the top of the compression stroke and made sure that the rotor points to the #1 plug yet. i plan on doing that next time i'm at the garage. somehow i knew you'd be the first to reply, TRBenj! |
Posted By: phatsat67
Date Posted: May-16-2016 at 2:37pm
| Money on you didn't put the new points spring and you're only putting pressure on the point via the brass connection ribbon. They will miss fire horribly at about 2300 rpms. If it didn't come with a spring take it off the old point and put it on the new one. |
Posted By: jtryon
Date Posted: May-16-2016 at 2:48pm
| I hope it's a simple as that. What does that spring look like? I replaced everything under the cap with the new components, so I didn't have a spring left over at least. I'll look through the old parts to see if the old one can be salvaged. |
Posted By: TRBenj
Date Posted: May-16-2016 at 3:23pm
I'm not sure what those numbers mean and it sounds like you don't either. Time to break out the timing light manual!If you are only getting 10 deg of advance (initial = 10 and final = 20) then I would expect the boat to run crappy but probably better than 2300rpm. What you're describing sounds more like a crossed plug wire, or perhaps what Zach is describing. The old points sets had the spring built in, the new ones it is a separate piece- but they don't look incomplete without it (the ground strap looks like and has *some* spring- but not enough at higher RPM). #1 cyl is unlikely to be off by a post or 2, it wouldn't run at all in that case. You also could not time it. I assume you are hooking the timing light to cyl #1. The firing order you listed is for a LH 351w, is that what you have? Describe what happens at 2300rpm? Just a lack of power? Does it stutter or hesitate? Backfire or misfire? |
Posted By: phatsat67
Date Posted: May-16-2016 at 3:26pm
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Yeah, what Tim said about the numbers. Maybe it's just the way you are wording it. If the spring isn't installed it's like a stutter rev limiter and it will not go above the offending rpm. With a stock dizzy 10 degrees initial should bet you anywhere from 28-31 degrees all in. All in is measured about 3000 rpms so you may be losing out on some advance due to the fact that you can't achieve 3000 rpms at the moment. Did you mean 580 rpms idle ? If so that makes sense but it slightly low. You want about 550-600 idle rpm underway in gear so that usually is 700-750 in neutral idle. |
Posted By: jtryon
Date Posted: May-16-2016 at 3:33pm
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one thing to mention is that there was a small "pad" which came with the points kit, which installs on the side of the points closest to the distributor shaft. here's a pic for reference: http://www.skidim.com/POINTS-PRESTOLITE-ALL/productinfo/R114002/ (sorry they wouldn't let me copy just the pic) i left that pad off because the old set didn't have that on there and i didn't know what it was for. would that cause problems? by "pad" i'm talking about the rectangular-looking item by the copper strap. i have a picture of my old points before i took them out, and they had a plastic piece installed over them which isn't on the new points. could the spring be a part of that? yes i'm hooking the timing light to cyl #1 (starboard front), and i have a LH 351W. at 2300 rpms it stumbles, hesitates, stutters, all of the above. no backfiring, but sounds more like a misfire. |
Posted By: phatsat67
Date Posted: May-16-2016 at 3:45pm
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Take pics of the old points and the new ones tonight. |
Posted By: jtryon
Date Posted: May-16-2016 at 4:05pm
here's the old points: of course the garage is in a different town than my condo, but i'll try to get there after work or tomorrow morning to take pics of the new points for comparison. |
Posted By: phatsat67
Date Posted: May-16-2016 at 4:15pm
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Ok, unless I'm missing something, the old point looks like the contact and the spring are one piece. On the pints you'll have a hard silver spring and a softer brass contact ribbon. They go to the same place but there should be two pieces. The brass is strong enough to make it run to about the rpm you're describing. The spring is removable on the new points but should have been included if you bought a pcm tune up kit. Was it running properly before ? |
Posted By: jtryon
Date Posted: May-16-2016 at 4:22pm
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IIRC there is only one spring on the new point, the hard silver spring. but since you said that, i seem to remember another one being in the package separately. i will take a look at the package to see if it's still in there. it was running somewhat properly before, i just had hot start issues and problems idling after the engine had been running for a while. that's why i got the carb rebuilt this spring because it was long overdue, as well as the points which i'm sure you can tell by looking at the above picture. |
Posted By: 63 Skier
Date Posted: May-16-2016 at 5:22pm
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By the looks of that distributor I think you need to pull the base and see if your advance weights are intact and operating OK. That might explain the lack of full advance. ------------- '63 American Skier - '98 Sport Nautique |
Posted By: 8122pbrainard
Date Posted: May-17-2016 at 12:44am
I did that once!! ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Gary S
Date Posted: May-17-2016 at 12:54am
What? you mean that one time you changed your points? You'll probably forget and do it again when you change them next time in 20 years  ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: 8122pbrainard
Date Posted: May-17-2016 at 7:18am
Notice I did say once!! ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Duane in Indy
Date Posted: May-17-2016 at 7:24am
Yea, the other times he tuned them up he installed a Pertronix kit. ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
Posted By: phatsat67
Date Posted: May-17-2016 at 10:04am
| Lol Pete. I've forgot to install it once or twice but never actually started the motor without it in ha. |
Posted By: 8122pbrainard
Date Posted: May-17-2016 at 10:22am
I did run the engine and yes, wondered why the engine wouldn't rev!! ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: jtryon
Date Posted: May-17-2016 at 10:43am
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I stopped at the garage this morning and took some pictures, and phatsat67 may win this one. Sure enough there is a strap that the kit came with that was packaged separately and is not installed, so I'm hoping that cures the problem. Here is a picture of the new points (with old condenser installed which I did while tshooting this):  And here's the strap I believe you're referring to?  Too bad the kit didn't come with instructions, I could have avoided hours of troubleshooting. Of course looking back on skidim's site, when you buy the points alone they have a note that says "The new points include an extra reinforcement strap shown in the photo. Make sure to use it or your points will float above 2500 rpm." The full tune-up kit doesn't have this note. I guess they assume that people still using points all know how to work with them
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Posted By: 8122pbrainard
Date Posted: May-17-2016 at 11:44am
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Josh, That's the strap (spring)!!! ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: jtryon
Date Posted: May-17-2016 at 11:48am
| i assume it will logically install in a notch in the points and bolt down where the condensor and brass strap bolt down. easy enough, now that i know. i'll let you guys know when i start it, i'm hoping that's all it was! |
Posted By: phatsat67
Date Posted: May-17-2016 at 12:52pm
| Boom |
Posted By: quinner
Date Posted: May-17-2016 at 1:14pm
So you fella's with points can't get it going without the strap on.........  ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1143" rel="nofollow - Mi Bowt |
Posted By: 63 Skier
Date Posted: May-17-2016 at 1:20pm
That was impressive Zach! Josh posts his issue, and 3 posts and 70 minutes later you post the solution. Gotta love it. ------------- '63 American Skier - '98 Sport Nautique |
Posted By: jtryon
Date Posted: May-17-2016 at 1:23pm
if only i had posted on here sunday when i was trying to figure it out! 
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Posted By: TRBenj
Date Posted: May-17-2016 at 1:45pm
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Nice one Zachy! I only made that mistake once, ha. |
Posted By: phatsat67
Date Posted: May-17-2016 at 1:50pm
| Haha thanks. I had a few boats come in customers tried to do points swaps on. Generally, if the thing runs good I don't even touch the points. Just cap and rotor slap and lube the weights and the the points cam and call it a day. |
Posted By: DrCC
Date Posted: May-17-2016 at 4:14pm
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WTH brand of points comes with the spring not attached or installed ??? |
Posted By: phatsat67
Date Posted: May-17-2016 at 4:22pm
| Pcm baby. |
Posted By: backfoot100
Date Posted: May-17-2016 at 4:38pm
Thank You....I was trying to make some sense of that one too. Never heard of such a piece of crap. No wonder guys want to change to EI modules. ------------- When people run down to the lake to see what's making that noise, you've succeeded. Eddie |
Posted By: Gary S
Date Posted: May-17-2016 at 4:56pm
Quinners motto ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: Gary S
Date Posted: May-17-2016 at 5:02pm
Anyone can get a Chevy to run Eddie Thats why the govt bailed them out they needed their voters to be able to go get their EBT cards  ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: backfoot100
Date Posted: May-17-2016 at 5:55pm
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Hmmmmmm....Good thought Gary. That 'splains why Ford isn't in the marine business anymore.... ------------- When people run down to the lake to see what's making that noise, you've succeeded. Eddie |
Posted By: Gary S
Date Posted: May-17-2016 at 11:45pm
Being on a fixed income now Eddie thats why I had to sell my Ford Volvo and buy a Avalanche  ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: 8122pbrainard
Date Posted: May-17-2016 at 11:51pm
And if I'm remembering correctly, the loose spring I encountered was on a set of Echlin's!! ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: jtryon
Date Posted: May-19-2016 at 11:08am
started the boat last night after adding the strap to the points and it revs up no problem now! thanks again guys for the help 
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