• Mustang Forums
  • 1974 - 1978 Mustang II Talk & Tech

Engine Intermittent Spark, no start

  • Thread starter Thread starter 1978Cobra2
  • Start date Start date Jan 22, 2019

1978Cobra2

Member
Mar 25, 2014
69
1
9
Jan 22, 2019
#1
  • Jan 22, 2019
  • #1
Hey everyone it's been a while. About lost all patience with my 78. So life's been busy for the last couple of years so the cars have been sitting around and not run much. Well I wanted to get my 78 running enough to move it around or drive it for a bit. It has not had a gas cap on it for a long time so the fuel tank pretty much was 50/50 water fuel... It would start right and run but very poorly and it would idle all day with the choke on. So I pulled the tank cleaned it out, cleaned the carb very well put it back on and it barely ran and was popping very loud out of the exhaust and shooting fire. It seemed like too much fuel so I got out and looked and sure enough after shutting it off fuel was dripping out of the secondary boosters. Took the needle and seat out cleaned it put it back in and it barely wanted to run at all. I started messing with float level after that figuring taking the needle out messed the adjustment up. It got to the point where the car wouldnt want to start at all. No fuel, a lot of fuel, it would crank all day and not start. I started chasing spark, put the timing light on and noticed it would only fire every few rotations. Used a spark tester to confirm. Long story short ive been pulling my hair out with this thing. It has a new cap, rotor, condenser, coil, and points which are adjusted to .020. It will spark about 4 times then nothing for a few rotations than back to sparking a few times. Watching the points they consistently seem to spark. Ive given the coil direct 12v and replaced the signal wire from distributor to coil. Every now and i mean very rarely it will start for maybe 5-10 seconds. Played with the timing and nothing helped, its set at about 8* right now

I'm at a total loss, how did a fuel issue turn into a spark problem after cleaning the water out?

The engine did kind of "explode" along the way... while adjusting the floats a lot of fuel was spilled and it popped out of the carb and light a few rags on fire which led to what i assume vapor build up under the valve cover to explode. It blew the valve cover right off the bolts... Regardless it is having the sames problems now as it did before that.

It's a 1973 302 with the stock points ignition. The carb is a Holley 4160

I'm pretty much out of options so any Ideas will help, Thanks!
 

LILCBRA

I wish I didn't have all of these balls in the air
Mod Dude
Dec 6, 2005
6,330
5,300
194
Corn County USA
Jan 23, 2019
#2
  • Jan 23, 2019
  • #2
After pulling my hair out over a very similar problem years ago, I found that I had the ground cable come loose for whatever reason - my suggestion would be chase grounds. Otherwise I'm at a loss, same as you. Maybe your plug wires have gone bad???? I mean if you have spark at the points every time but only intermittently at the plug, that's about the only connection between the 2 as long as the new cap and rotor is good. Check grounds first as it shouldn't cost you anything but time and go from there. Let us know what you come up with - good luck!!
 

1978Cobra2

Member
Mar 25, 2014
69
1
9
Jan 24, 2019
#3
  • Jan 24, 2019
  • #3
Went out the other night and didnt change anything but it had spark everytime at the tester. The spark looks weak at the plug though. Checked grounds today, everything seems fine. Used jumper cables both from negative side to engine block and tried it. No sign of life. I give the carb three pumps but after so long of cranking it smells like there's a fuel leak. The plugs are dry though. I need a break from this thing!
 

2Blue2

will be trying this sex one when I can find it
Mod Dude
Mar 5, 2019
4,430
2,893
163
Oahu
Mar 5, 2019
#4
  • Mar 5, 2019
  • #4
If the valve cover blew off, check the oil for gas contamination. A couple of gals of gas in the crankcase could be problematic for starting.
Points suck maybe a pertronix in in your future
 

1978Cobra2

Member
Mar 25, 2014
69
1
9
Mar 6, 2019
#5
  • Mar 6, 2019
  • #5
It sorta had the issue before the valve cover blew off, then again it all started after it was flooded so ill have to check. Ive looked at a new ignition system and will probably go that route soon. I haven't touched the car in a while but I am planning on a compression test next. Thanks for the ideas!
 

1978Cobra2

Member
Mar 25, 2014
69
1
9
Mar 24, 2019
#6
  • Mar 24, 2019
  • #6
Ok, update. Got some time to mess with the car, did a compression test and it was cranking way slow even with all the plugs out. Got really low numbers 100-110 on all cylinders but blamed it on the slow crank. Oil seemed high and smelled like gas, drained it and ended up with about 9qts coming out... Put fresh oil in and still no fire but cranks normally now! thanks for the help on that one. I recleaned and gaped the points and it fired for 10 seconds and had no other life after that. I figure it had to be something with the points if it runs for a few seconds everytime i tune them in. My buddy ended up letting me borrow his Pertronix point delete and the thing fires right up no problem even in the cold. I dont know what the issue with the points were but this pertronix solved it immediately. So ill be buying my own now.

Thanks all for the help!
 

2Blue2

will be trying this sex one when I can find it
Mod Dude
Mar 5, 2019
4,430
2,893
163
Oahu
Mar 25, 2019
#7
  • Mar 25, 2019
  • #7
1978Cobra2 said:
Thanks all for the help!
Click to expand...

I'm glad its headed toward working better. If the inlet needle on carb sticks the gas fills carb and overflows into crankcase, check your carb float inlet needle!
 
You must log in or register to reply here.

Similar threads

A
1987 5.0 speed density Foxbody crank no start
  • Alan2204
  • May 23, 2026
  • Fox 5.0 Mustang Tech
Replies
10
Views
152
Fox 5.0 Mustang Tech May 30, 2026
Mcmahst
F
1986 mustang no start
  • foxyjamss221
  • Oct 11, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
4
Views
296
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Oct 13, 2025
foxyjamss221
F
96 GT 4.6 w/ dirty spark plug well
  • Mustang Momma
  • Apr 7, 2026
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
3
Views
104
1996 - 2004 SN95 Mustang -General/Talk- Apr 9, 2026
LILCBRA
L
Engine Why won't the motor start if I have spark and fuel
  • LeviAnderson
  • Nov 20, 2025
  • Fox 5.0 Mustang Tech
Replies
3
Views
385
Fox 5.0 Mustang Tech Nov 20, 2025
AeroCoupe
K
Electrical 2000 GT Intermittent Engine Shutdown In Motion - DTC U1262
  • kenster1092
  • Apr 13, 2026
  • SN95 4.6L Mustang Tech
Replies
4
Views
136
SN95 4.6L Mustang Tech Apr 24, 2026
squeak93
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1974 - 1978 Mustang II Talk & Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?