Engine breaking up at about 2500 rpm.

Hitman84 · 08-15-2008, 11:51 AM

I want to pick some brains here. My car was running great until about 3 weeks ago. My engine idles great, but when you get it under a load is starts to break up or sputter from 2500 rpm through the rest of the power band. I have replaced plugs, checked plug wires, tested my msd box and coil, and my timing. I have also checked compression in all cylinders and they are all perfect. I have verified (to the best of my ability) that there is no float of any valves. The only thing on my motor that is not brand new is the Mechanical fuel pump.

My question is, what is the possability that my pump fails at higher rpm. Is there something I am forgetting to check?

Also should mention that when I put the motor in, I added one of those clear glass fuel filters inline between the pump and the carb. At start up the filter is full of fuel, after driving 60 feet and back into the driveway the filter is less than half full, not sure if this is normal, but may help deduce if the pump is bad.

Thanks for any help.

**Sonic Blue 85** · 08-15-2008, 02:14 PM

What are you running for spark plugs? If you have any brand of platinum plug repace them with copper plugs, also Fords do not like Bosch or Champion plugs of any type. Have you checked the fuel level in the fuel bowls or pulled the carb apart to make sure there is not any trash in the carb?

Hitman84 · 08-15-2008, 02:21 PM

i was running NGK vpower plugs, but i changed to good old reliable autolite 25's last night and it helped a little, but still the same. i have not pulled the carb apart (kind of hesitant to do so since it is brand new) the fuel level in the bowls is right at the bottom of the window where the Holley manual says it should be.

can i pull the carb apart without messing anything up? all i know to do is pull the bowls off and the base plate. that is the extent of my carb knowlege.

keg65 · 08-16-2008, 05:55 AM

maybe you got some bad gas?

craiger · 08-16-2008, 05:16 PM

Does this do this right away after start up or after the car is warmed up? My thought is maybe it is the Converter is clogged up. Also, check the distributor's module, and MAF.
Good Luck.

Hitman84 · 08-18-2008, 10:13 AM

Quote:

Originally Posted by craiger

Does this do this right away after start up or after the car is warmed up? My thought is maybe it is the Converter is clogged up. Also, check the distributor's module, and MAF.
Good Luck.

car is carbed, so it has no MAF. i am running a full MSD Ignition with pro billet distributor and all checked out fine.

Quote:

Originally Posted by keg65

maybe you got some bad gas?

This was my first thought. but i have cycled two different types of gas and i get the same with both. both are 93 octane.

I bought a new electric pump and regulator and that will go on this weekend. hopefully this fixes the problem.

tulabeast · 08-18-2008, 08:14 PM

drink a beer and think of the good times

thatdavidkid · 08-18-2008, 08:42 PM

Quote:

Originally Posted by Hitman84

I bought a new electric pump and regulator and that will go on this weekend. hopefully this fixes the problem.

that is what i would have recomended... 2500 sounds high to start bogging out, but who knows... i assume you dont have a fuel pressure guage? i guess with a mechanical pump, it could be something odd at 2500 it floats or something... let us know how it turns out w/ the new pump

Hitman84 · 08-19-2008, 11:21 AM

Quote:

Originally Posted by tulabeast

drink a beer and think of the good times

AMEN!!!!!!

Hitman84 · 08-25-2008, 04:16 PM

well, i upgraded my entire fuel system up to the carb. got a good deal on a Holley blue and regulator. installed new 3/8 line all the way. new AN fittings with a steel braided fuel line at the carb. adjusted the pressure to about 7.5 psi. and adjusted the floats and idle on the carb.

She runs like a scolded dog!! Awesome!!! Next, a new set of heads to replace my E7's.

08-15-2008, 11:51 AM	#1
Hitman84 Registered User Join Date: Mar 2008 Location: Galveston County Posts: 98 Trader Rating: (1)	Engine breaking up at about 2500 rpm. I want to pick some brains here. My car was running great until about 3 weeks ago. My engine idles great, but when you get it under a load is starts to break up or sputter from 2500 rpm through the rest of the power band. I have replaced plugs, checked plug wires, tested my msd box and coil, and my timing. I have also checked compression in all cylinders and they are all perfect. I have verified (to the best of my ability) that there is no float of any valves. The only thing on my motor that is not brand new is the Mechanical fuel pump. My question is, what is the possability that my pump fails at higher rpm. Is there something I am forgetting to check? Also should mention that when I put the motor in, I added one of those clear glass fuel filters inline between the pump and the carb. At start up the filter is full of fuel, after driving 60 feet and back into the driveway the filter is less than half full, not sure if this is normal, but may help deduce if the pump is bad. Thanks for any help. __________________ '84 fox convertible. E7 roller block .030 over with Hyper. pistons and stock stroke for now. E7 heads, Weiand Stealth intake, holley 4777, comp cams magnum 290 cam and springs, and complete MSD ignition. MAC equal length shorty headers to BBK O/R X-pipe to dual chamber flows. Electric fan conversion. '92 silver ponys. Just added, UPR non adjustable upper and lower control arms, Eiback Pro drop springs, MGW short throw shifter, billet overflow tank, and a few other billet accessories.

08-15-2008, 02:14 PM	#2
Sonic Blue 85 LSS Sponsor Join Date: Dec 2007 Location: New Braunfels Posts: 393 Trader Rating: (1)	What are you running for spark plugs? If you have any brand of platinum plug repace them with copper plugs, also Fords do not like Bosch or Champion plugs of any type. Have you checked the fuel level in the fuel bowls or pulled the carb apart to make sure there is not any trash in the carb? __________________ My car is an '85 sonic blue coupe with 302 bored and stroked to 364, Ported Twisted Wedge heads and a BXR intake, A9M ECM with a Tweecer, C4 with trans brake, Hoosier 275/60/15 drag radials, no power adders. The car is still street driven, with a best of 10.21 at 131 mph with a 1.51 60' spinning lightly. With this combo it made a best of 460 hp and 410 lbs of torque at the wheels.

08-15-2008, 02:21 PM	#3
Hitman84 Registered User Join Date: Mar 2008 Location: Galveston County Posts: 98 Trader Rating: (1)	i was running NGK vpower plugs, but i changed to good old reliable autolite 25's last night and it helped a little, but still the same. i have not pulled the carb apart (kind of hesitant to do so since it is brand new) the fuel level in the bowls is right at the bottom of the window where the Holley manual says it should be. can i pull the carb apart without messing anything up? all i know to do is pull the bowls off and the base plate. that is the extent of my carb knowlege. __________________ '84 fox convertible. E7 roller block .030 over with Hyper. pistons and stock stroke for now. E7 heads, Weiand Stealth intake, holley 4777, comp cams magnum 290 cam and springs, and complete MSD ignition. MAC equal length shorty headers to BBK O/R X-pipe to dual chamber flows. Electric fan conversion. '92 silver ponys. Just added, UPR non adjustable upper and lower control arms, Eiback Pro drop springs, MGW short throw shifter, billet overflow tank, and a few other billet accessories.

08-16-2008, 05:16 PM	#5
craiger Craiger Join Date: Jul 2008 Location: Austin, Texas Posts: 13 Trader Rating: (0)	Does this do this right away after start up or after the car is warmed up? My thought is maybe it is the Converter is clogged up. Also, check the distributor's module, and MAF. Good Luck. __________________ 1989 GT Convert. 5.0

08-18-2008, 08:14 PM	#7
tulabeast always asleepn Join Date: Feb 2006 Location: ingram park sucka Posts: 924 Trader Rating: (0)	drink a beer and think of the good times __________________ 91 lx not on the sidelines anymore baby} 98 gt on the streets. mod motors suk MAD PROPS 2 AnR GOT BOTH MY BEAST RUNNING GOOD.

08-16-2008, 05:55 AM	#4
keg65 Change always makes Sense (or Cents) Join Date: May 2005 Location: NE San Antonio Posts: 1,275 Trader Rating: (0)	maybe you got some bad gas?

08-25-2008, 04:16 PM	#10
Hitman84 Registered User Join Date: Mar 2008 Location: Galveston County Posts: 98 Trader Rating: (1)	well, i upgraded my entire fuel system up to the carb. got a good deal on a Holley blue and regulator. installed new 3/8 line all the way. new AN fittings with a steel braided fuel line at the carb. adjusted the pressure to about 7.5 psi. and adjusted the floats and idle on the carb. She runs like a scolded dog!! Awesome!!! Next, a new set of heads to replace my E7's. __________________ '84 fox convertible. E7 roller block .030 over with Hyper. pistons and stock stroke for now. E7 heads, Weiand Stealth intake, holley 4777, comp cams magnum 290 cam and springs, and complete MSD ignition. MAC equal length shorty headers to BBK O/R X-pipe to dual chamber flows. Electric fan conversion. '92 silver ponys. Just added, UPR non adjustable upper and lower control arms, Eiback Pro drop springs, MGW short throw shifter, billet overflow tank, and a few other billet accessories.

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