PDA

View Full Version : No spark at cylinders 4 & 8 on 351W


jsnyng23
09-08-2011, 10:53 AM
Hi Guys,

Long time reader, first time poster!

I've tried to find the answer to my issue by checking archived threads but nothing I've found fits my exact issue.

Anyway, I have a 1988 ProStar 190 with a 351W that I just bought this summer. The main issue I've been chasing all summer is that I have not been able to get the boat over 2800 RPM's & approx 36 MPH when under load. Sitting in neutral, I can rev it over 4000 RPM's with no issues.

The boat had been sitting in storage for the past 2 years when I bought it, so I've been going through it each weekend replacing/repairing things I've read on these forums that should be done. The following is everything I've done so far:
- Rebuilt the carb (Holley 4160)
- New Plugs
- New dist. cap & rotor (boat has electronic ignition. timing advance springs are rusty but
not seized.)
- Set timing at 10 deg BTDC
- New fuel filter & fuel/water sep filter
- New ignition coil (automotive type - not sure if this needs to be marine grade)
- New starter solenoid
- New starter (replaced with same automotive starter that was on it but will be changing to
marine grade starter after having just come across a forum thread telling of the
dangers of using the wrong starter)
- Aligned motor, drive shaft & strut (strut was bent 1/2" off center - new bushings in strut on
re-install)

All that, and the problem still remains.

Last night, I went back to the engine with plans of checking spark at all plugs & then compression. I got as far as pulling all the plugs & have found that the plugs in cylinders 4 & 8 look just as new as when I put them in about 6 weeks ago. It appears as though they have never fired. Although I no doubt need new plug wires, I have confirmed that all the wires will deliver spark when swapped around on the distributor cap. What I have found is that regardless of what plug wire I use on the distributor I cannot get spark from the distributor positions for cylinders 4 & 8.

I still plan to check compression in the next couple of days, as well as replace the plug wires, but I no doubt have an electrical issue.

Any help with ideas of where to go next would be greatly appreciated!

Jorski
09-08-2011, 11:56 AM
Sounds like something is wrong with the distributor.

I am sure someone will chime in with a more detailed analysis...but I would start there.

rjracin240
09-08-2011, 12:59 PM
Definitely would be looking at the distributor cap, try doing a continuity check from the inside post on 4 & 8 to the outside where the wires plug in, also check for cracks or carbon trails on the inside of the cap where there could be a ground allowing the cap to short. Thinking that if you had loss of compression on those cylinders there might be secondary indications. got my fingers crossed that it is just the cap. know you have already replaced cap and rotor, sometimes you might have already fixed the original problem and then created a new one at the same time.

Look into DB Electrical for new starter (appx $75 for marine starter) put one on my 88 190 last year as well as replaced battery cables....BIG Difference

Good Luck

Dino Don
09-08-2011, 04:03 PM
Hi Guys,

Last night, I went back to the engine with plans of checking spark at all plugs & then compression. I got as far as pulling all the plugs & have found that the plugs in cylinders 4 & 8 look just as new as when I put them in about 6 weeks ago. It appears as though they have never fired. Although I no doubt need new plug wires, I have confirmed that all the wires will deliver spark when swapped around on the distributor cap. What I have found is that regardless of what plug wire I use on the distributor I cannot get spark from the distributor positions for cylinders 4 & 8.

I still plan to check compression in the next couple of days, as well as replace the plug wires, but I no doubt have an electrical issue.

Any help with ideas of where to go next would be greatly appreciated!

You need that compression test--real low compresseion or no compression it will not fire on those cylinders. Usually min. is 90 lbs on a cylinder for it to hit.

jsnyng23
09-08-2011, 04:42 PM
Thanks! I'll take a look at that tonight.

tommcat
09-08-2011, 04:44 PM
exactly how are you checking for spark?

jsnyng23
09-08-2011, 05:00 PM
I agree that I still need to do the compression test but won't be able to get to it until Friday night or Saturday morning. To clarify, though, I checked for spark on each plug 1 at a time with them out of the engine. I just did a quick check with a plug attached to a plug wire held up against metal & cranked the engine. In doing so, I noticed spark on each plug & wire combination except for the 2 that go to cylinders 4 & 8 from the distributor cap connection points. Regardless of which plug wires I hooked up to those 2 connection points, I saw no visible spark from the plugs. The same wires hooked up to any other distributor connection point would produce visible spark with any plug I attached to it.

Again, I will definitely do the compression test to rule out any issues there, but in my thinking I believe the lack of spark in the manner in which I checked for it is independent of a compression issue. Am I wrong or missing something?

thatsmrmastercraft
09-08-2011, 05:06 PM
Spark or no spark is independent of compression. Sounds like you need a new distributor cap and rotor. You could have a problem with your electronic ignition, but they usually work or don't work - seldom anything in between. You might also check the cam on the dist. shaft. Never heard of it, but I suppose it could get rounded and fail to trigger a spark.

jsnyng23
09-08-2011, 05:21 PM
Cap & rotor are new, but I am going to do a continuity check per the reply from rjrancin just to be sure there are no issues with the cap. I haven't physically pulled the whole distributor up to this point but will do so & take a look. Relative to an ignition issue, do you know if the ignition module/magnetic pick-up that is under the rotor can cause an isolated lack of spark?

gr82bgreen
09-08-2011, 05:34 PM
A badly worn dist shaft may cause a loss of spark at 1 or more cylinders. See if you can wiggle the shaft at the rotor. Using the method you did it would have to be the plug, wires, cap or dist. compression has nothing to do with creating spark outside the engine. But yes do the compression test as well.

CantRepeat
09-08-2011, 05:45 PM
You need that compression test--real low compresseion or no compression it will not fire on those cylinders. Usually min. is 90 lbs on a cylinder for it to hit.

Compression has nothing to do with getting spark. It might be needed for combustion, but I doubt that too. Fuel and air will burn regardless if it is compressed or not.

There has to be something grounding out in the distributor for it not to send spark to just two cylinders.

tommcat
09-08-2011, 06:04 PM
Compression has nothing to do with getting spark. It might be needed for combustion, but I doubt that too. Fuel and air will burn regardless if it is compressed or not.

There has to be something grounding out in the distributor for it not to send spark to just two cylinders.

actually compression is needed for combustion. otherwise you dont get an explosion, just a little fire.

but i'd like to know what method is being used to determine there is no spark to be sure that is actually the(or a) problem.

tommcat
09-08-2011, 06:07 PM
I agree that I still need to do the compression test but won't be able to get to it until Friday night or Saturday morning. To clarify, though, I checked for spark on each plug 1 at a time with them out of the engine. I just did a quick check with a plug attached to a plug wire held up against metal & cranked the engine. In doing so, I noticed spark on each plug & wire combination except for the 2 that go to cylinders 4 & 8 from the distributor cap connection points. Regardless of which plug wires I hooked up to those 2 connection points, I saw no visible spark from the plugs. The same wires hooked up to any other distributor connection point would produce visible spark with any plug I attached to it.

Again, I will definitely do the compression test to rule out any issues there, but in my thinking I believe the lack of spark in the manner in which I checked for it is independent of a compression issue. Am I wrong or missing something?and dont take this the wrong way, but which cylinders(location on the engine) are you calling 4 and 8?
did you check for spark coming right out of the dist cap? you can just loosen the wire a bit to back it out of the cap slightly and crank to see if it sparks there. it should be a bright, clean spark that you can clearly hear snap.

jsnyng23
09-08-2011, 06:46 PM
No problem......cylinder 4 = last cylinder on RH (driver) side & cylinder 8 = last cylinder on LH (pass side). I have not checked for spark as you described directly out of the top of the dist cap. I have checked each plug & wire combination still connected to the cap but out of the engine and resting against something metal (wrench) while cranking the ignition. I've done this for each plug 1 at a time with all others still attached to dist & in engine. I've even swapped wires to confirm the wires work. All the wires deliver spark to an uninstalled plug, except when plugged into the dist at the terminals that lead to cylinders 4 & 8. Regardless of what plug and wire combination I use there, I cannot get visible spark.

tommcat
09-08-2011, 07:01 PM
No problem......cylinder 4 = last cylinder on RH (driver) side & cylinder 8 = last cylinder on LH (pass side). I have not checked for spark as you described directly out of the top of the dist cap. I have checked each plug & wire combination still connected to the cap but out of the engine and resting against something metal (wrench) while cranking the ignition. I've done this for each plug 1 at a time with all others still attached to dist & in engine. I've even swapped wires to confirm the wires work. All the wires deliver spark to an uninstalled plug, except when plugged into the dist at the terminals that lead to cylinders 4 & 8. Regardless of what plug and wire combination I use there, I cannot get visible spark.
ok, you do have your cylinders correct. a lot of people get that wrong, that's why i asked.

basically if you have spark at all the other holes and the wires work fine you should be ok on the ignition secondary side. you could either have a bad dist cap or some type of pickup issue. check inside the cap carefully to make sure there are no cracks that could allow the spark to travel to ground instead of through your wire, moisture can do the same thing. i know your cap is new but i've had plenty of them come off out of the box with problems. the fact that 4 and 8 are next to each other on the cap could easily allow a problem there.

as far as the pickup is concernd you'll need a DVOM to diagnose that part. what type of ignition system is it?

and just to double check, is this how it's wired?

jsnyng23
09-08-2011, 07:09 PM
I'm just leaving work for home so I'll check and report back in an hour or 2.

jsnyng23
09-11-2011, 03:35 PM
Update:
- Checked compression > all cylinders 130 - 140 psi
(this was done with cold engine & all plugs out. was only looking for major differences
from cylinder to cylinder but found all to have similar psi readings)
- Distr cap inspected for cracks/damage with no defects found inside or outside
(just to reiterate this is a new cap & rotor & the symptoms I am having were present
with old cap & rotor)
- Pulled distributor from engine to inspect for damage/defects & found no damage to gear and
no excessive play when installed. Distributor is a prestolite
- Determined type of electronic ignition to be a pertronix ignitor.

Not sure where to go next except for checking the ignition pickup as suggested by TOMMCAT but not exactly sure what I'm looking for there.............

JimN
09-11-2011, 04:01 PM
Cap & rotor are new, but I am going to do a continuity check per the reply from rjrancin just to be sure there are no issues with the cap. I haven't physically pulled the whole distributor up to this point but will do so & take a look. Relative to an ignition issue, do you know if the ignition module/magnetic pick-up that is under the rotor can cause an isolated lack of spark?

A continuity test won't necessarily tell you if the plugs will fire when it's running because you'll be testing for DC continuity and at high speeds, each cylinder is firing at 3KHz-5HKZ.

The pickup coil/reluctor can cause problems like this but usually, it wither provides spark, or not.

You didn't change the plug wires- why not? If they're more than a few years old, they're too old, especially if the boat runs for more than 100 hours/season. You may have spark when you pull them off of the plugs but that's not the normal position and you may be causing them to provide enough continuity. Also, the spark you're seeing may not be intense enough to fire them when they're in place.

jsnyng23
09-11-2011, 04:28 PM
Not changing the plug wires was an oversight on my part as I should have thought to change them when I replaced the cap & plugs. I'll have new ones from skidim this week.

When I've checked for visual spark, I have done it with a wire attached to a plug & the plug outside of the engine. I have confirmed that the wires going to cylinders 4 & 8 provide visible spark to a plug when moved to another position on the dist cap.

JimN
09-11-2011, 04:48 PM
Not changing the plug wires was an oversight on my part as I should have thought to change them when I replaced the cap & plugs. I'll have new ones from skidim this week.

When I've checked for visual spark, I have done it with a wire attached to a plug & the plug outside of the engine. I have confirmed that the wires going to cylinders 4 & 8 provide visible spark to a plug when moved to another position on the dist cap.

You know that you can buy plugs, wires, cap, rotor and most engine parts from a local car parts dealer, right? When I buy parts like these, I get the ones with lifetime warranty.

tommcat
09-11-2011, 05:04 PM
Update:
- Checked compression > all cylinders 130 - 140 psi
(this was done with cold engine & all plugs out. was only looking for major differences
from cylinder to cylinder but found all to have similar psi readings)
- Distr cap inspected for cracks/damage with no defects found inside or outside
(just to reiterate this is a new cap & rotor & the symptoms I am having were present
with old cap & rotor)
- Pulled distributor from engine to inspect for damage/defects & found no damage to gear and
no excessive play when installed. Distributor is a prestolite
- Determined type of electronic ignition to be a pertronix ignitor.

Not sure where to go next except for checking the ignition pickup as suggested by TOMMCAT but not exactly sure what I'm looking for there.............

i would check the pickup with a graphing DVOM but i dont think most people have those. the easy way to check would be to pull out the distributor, leave it hooked up electrically but you dont need the cap or any wires on it. hook one wire to the coil and put a plug in the end of it. spin the distributor by hand and see if you get a spark through the whole 360 degrees of dist rotation. if not you could have a bad spot in it.
as jim said, that would be pretty rare since they usually work or they dont but it is possible to have one fail like that.

tommcat
09-11-2011, 05:06 PM
You may have spark when you pull them off of the plugs but that's not the normal position and you may be causing them to provide enough continuity. Also, the spark you're seeing may not be intense enough to fire them when they're in place.

jim, he isnt having the problem of visible spark but not firing the cylinder. he doesnt have spark at all at cyl 4 and 8

jsnyng23
09-11-2011, 05:10 PM
Yes & good point! Sometimes I'm thinking "marine" parts & forget that most are just "truck" parts. Thanks for the reminder!

jsnyng23
09-11-2011, 05:17 PM
i would check the pickup with a graphing DVOM but i dont think most people have those. the easy way to check would be to pull out the distributor, leave it hooked up electrically but you dont need the cap or any wires on it. hook one wire to the coil and put a plug in the end of it. spin the distributor by hand and see if you get a spark through the whole 360 degrees of dist rotation. if not you could have a bad spot in it.
as jim said, that would be pretty rare since they usually work or they dont but it is possible to have one fail like that.
I fall in the most people category as I don't have a graphing DVOM. I will do the manual check that you suggest though. Heading to the boat to try it now.

tommcat
09-11-2011, 05:21 PM
and one thing to keep in mind for everyone doing plug wires on a 351 is to not route wires for cylinders 6 and 5 next to each other. they can actually induce a crossfire condition which can break pistons, rings and melt valves.

jsnyng23
09-11-2011, 05:42 PM
i would check the pickup with a graphing DVOM but i dont think most people have those. the easy way to check would be to pull out the distributor, leave it hooked up electrically but you dont need the cap or any wires on it. hook one wire to the coil and put a plug in the end of it. spin the distributor by hand and see if you get a spark through the whole 360 degrees of dist rotation. if not you could have a bad spot in it.
as jim said, that would be pretty rare since they usually work or they dont but it is possible to have one fail like that.
I just went out & gave that a try & unless I was doing something wrong, I am getting no spark at all.

I pulled the distributor from the engine and with cap off, I hooked 1 wire to the coil & the other to a plug touching a metal wrench, and then spun the gear on the distributor by hand. I saw no visible spark. I tried with the ignition key off and then on. Battery is in & fully charged.

Am I not doing something correct?

tommcat
09-11-2011, 08:23 PM
I just went out & gave that a try & unless I was doing something wrong, I am getting no spark at all.

I pulled the distributor from the engine and with cap off, I hooked 1 wire to the coil & the other to a plug touching a metal wrench, and then spun the gear on the distributor by hand. I saw no visible spark. I tried with the ignition key off and then on. Battery is in & fully charged.

Am I not doing something correct?you have the primary ignition wires hooked up from the dist pick up, ignition module to the coil? ignition turned on, you may need to ground the distributor housing but i'm not 100% sure with that ignition system

ahhudgins
09-11-2011, 09:27 PM
When you say that the engine will rev up to 4000 RPMs in neutral “with no issues”, is there a mis in the engine and how does it idle? If two cylinders were actually not firing it should idle and run like crap. I’m surprised that you are getting 36 MPH at only 2800 RPM unless you are having some issues with your speedo or tach.

I’m not 100% familiar with that ignition but I would be checking the gap on the pickup at EACH firing position. I would also remove the cap and check the rotor height around the entire range of motion.

What does the spark pattern look like on the contacts inside the new and old distributor caps? Has the rotor been running across the middle of the contacts or just barely on the bottom?

JimN
09-11-2011, 10:13 PM
I just went out & gave that a try & unless I was doing something wrong, I am getting no spark at all.

I pulled the distributor from the engine and with cap off, I hooked 1 wire to the coil & the other to a plug touching a metal wrench, and then spun the gear on the distributor by hand. I saw no visible spark. I tried with the ignition key off and then on. Battery is in & fully charged.

Am I not doing something correct?

The coil and ignition system won't do anything unless you connect it to a source of current and even if the coil was still connected to the ignition wire, touching the plug to a wrench will do nothing if it's not grounded to the engine or directly to the battery. If the key is off, none of this will work.

Look at the underside of the new cap, at the center. Do you see a dark gray button that's spring-loaded? If not, look for it in the box the cap came in. This is absolutely necessary for the spark to transfer to the plug wires. If the center electrode is firmly in place, make sure the rotor is the right part- I have received the wrong part several times when ordering over the phone. If the new parts don't look identical, except for color, call the place you bought the parts from and have them re-check the part numbers/descriptions.

Hollywood
09-12-2011, 01:50 PM
I try not to be a parts changer but I would have just purchased a new distributor a long time ago.

I have a distributor you could borrow if you wanted.

chico
09-12-2011, 02:07 PM
When the engine is running,take a hammer handle and pry between the distributor and the intake manifold,if it clears up replace the distributor.

tommcat
09-12-2011, 02:14 PM
When the engine is running,take a hammer handle and pry between the distributor and the intake manifold,if it clears up replace the distributor.or, when the engine is running smash the he// out of the distributor until it stall, then replace the distributor8p

just kiddin, dont do that

thatsmrmastercraft
09-12-2011, 02:19 PM
or, when the engine is running smash the he// out of the distributor until it stall, then replace the distributor8p

just kiddin, dont do that

I'm sure use of the tuning hammer has crossed his mind by now. Unfortunately, the BFH doesn't always resolve issues as well as one would like.