new motor, BIG PROBLEMS why won't you run?

So the new 5.0 is in, all hooked up (Bought a rebuilt short block, .040 over). I pretty much replaced everything. New e cam, cast heads, wires, plugs, lifters, timing set, etc..

It will turn over and start for about a second or two, then die. I can get to run a little longer but you have to pump the hell out of the pedal, and it backfires, but not like a full out backfire, more of a pop.

Heres what i've tried, and hopefully ruled out.

1. Checked and rechecked the CPS with the tool and cyl. 1 location (tdc)
2. Checked all harnesses and all sensors
3. Checked for fuel at the rails
4. Making good oil pressure even when cranking over (40psi)
5. All vac lines are hooked up.

I was pretty thurough with setting the lifter preload, making sure i left no loose ends with wire harnesses, everything.

It seems to me like a timing issue, the backfire being fuel in the cylinder that is not on the power stroke (wasted spark system) I'm out of ideas.. I consider myself pretty mechanically inclined, and I just can't seem to figure out what i'm missing.

So i think i've got it down to a fuel timing issue, it won't idle, but will rev up, although, holding the throttle steady will not run either. The poping is excess fuel in the 2nd cyl being fired. I bought another CPS and reset it 2 more times, starting with TDC on the compression stroke. I'm TOTALLY out of ideas.

don't mean to sound stupid, but did you check your firing order? i cant remember what years it was, but you could use a 302 firing order, or a 351w firing order. long shot, but you never know.

The 5.0 explorers have the 351/302ho firing order 1,3, etc. Checked that, the e cam i put in also matches the firing order. It will rev up, but as soon as you stop dumping fuel, it dies out. I've tried putting the CPS in every which way, still nothing. Removed the crank sensor, and it will just crank, not fire, so it is working or at least doing something.

I would look at the plug wires really hard, and more and more. The pattern on the coil packs is not marked and extremely easy to mix up.
The firing order is the Cleveland firing order(first V8 to use it), 13726548. Try to view some pictures of other engines, did you take some before you started? The coil packs are not well designed IMO.

I read that you checked the CMP many times, that would have been my next place to look. You did find TDC by feeling for compression in the #1 cylinder yes, not by the balancer alone? The lifters don't have an adjustment, unless you used adjustable roller rockers. The lifter preload should be about about 0.035 when the cam is off of the lobe.

I checked for tdc every time with a piece of wire in the spark plug hole, and then verified with the balancer, both matched up everytime. I have accel coil packs, and made custom plug wires this time. Also i used my chiltons to verify the wires on the right packs, right locations, etc.

As for the rocker arms, you have to shim the ped. rocker so that there is between .020 and .060 of preload on the lifter. Or once the pushrod is just sitting tight between the rocker arm and lifter, it takes from 1/4 to 1 full turn to reach 20ft lbs of torque. (Ped. mounting bolt)

I think that you have the plug wires right, using a manual should get that done. Your lifters are likely fine. If they really are the stock rockers then the preload kit parts/shims are not something to do without careful work. For most cams like the Ford letter cams you should be able to bolt the stock parts down with no issues. Doing the preload is a nice step of blue printing, but it can be messed up. It sounds like you had a grasp of how it's done. The whole point of doing the valvetrain is to make sure the rockers go the same distance to each side of the valve tip, and that hydraulic lifters have some preload. Doing the preload is easy as you likely figured out. The pushrod length and rocker height controls the rocker relationship to the valve. Hopefully you didn't use many shims to alter what should be a bolt down combination. It is possible to get the rockers off to one side or the other of valves too far. That usually turns up at WOT and top rpm though, that shouldn't be your current symptoms(unless some valves are not closing).

You need to do the CMP again, you have only a 50% chance of it being right as you did it. The TDC of the #1 piston comes up twice during one cycle of the engine, these are four cycle engines. The CMP must be set on the compression stroke TDC of the #1 cylinder. Pull the plug, simply put a finger lightly into the hole. Turn the crank until you reach the timing marks on the balancer. If there is no pressure against your finger, the valves are open on the exhaust stoke, and that is not the right cycle. You need to have pressure observed on your finger and then locate the balancer there on the pointer at the TDC mark. Hopefully that's what you need to get it running right. Do the CMP first and hope that you have it out 180 degrees.

I wish it was.. I did that to make sure i was on the compression stroke I threw a vacuum gauge on just for the hell of it. Although it's not at a full idle, (only runs for a second or 2) it gets up to 20-25 in.. That leads me away from an intake leak. Also it should run with an intake leak, even a severe one, like crap of course. I've put a fuel pressure gauge on the fuel rail and it is making good pressure, even when i rev it up, the pressure doesn't drop.

It's late now, hopefully someone else will also have ideas. We'll think on it some more, night.

compression, fuel , spark



do a compression check with all plugs out

whats the fuel pressure, does the fuel shoot pretty far from the fuel rail valve?

if you hook up a LED 12v test light or noid light to injector plugs does it flash?

hook up a code reader after disconnecting the battery,reconnect then cranking for several seconds


spray carb cleaner thru the brake booster vacuum hose off the firewall for a few seconds if its a fuel issue, it should fire and run for several seconds.


if none of this works you ####ed up the timing somewhere or loose connector maybe

Hmmmm....it does run...but doesn't idle? And it pops? Through the exhaust or intake?

How do you know it's #2 causing the back fire?

This really sounds like a valve(s) hanging open. Did you prelube the engine prior to starting it? This would be an excellent time to do a compression check and see what you get.

After that, here is where I would be with this if this were mine...and I've been here with this exact problem. Pull the rocker covers. Let's inspect the valve train. Rotate the engine over and watch each and ever valve. Do they all move without hanging up somewhere? With new or reman heads, it's very easy for them to get a guide a bit snug and have it seize in the valve guide...even with brass guides. That's why you will see guys start a car with a new valve job by introducing just a bit of ATF into the engine (like Seafoam). It will prevent the valves from sticking until oil gets up there. Let's hope that isn't your problem.

The more likely problem is your valve adjustment. I want you to ignore all that .020 to .060 crap. Unless you can physically measure the plunger movement, you have no idea of what is actually moving when you tighten down a pedestal bolt. Here is a method that I have never, ever had fail me. First, mark your balancer every 90 degrees. It doesn't have to be dead accurate...just close. Start with #1 on compression. Verify by watching the intake valve on #1 close as the piston rises. Don't shoot me here...but remember, this isn't a Chebbie...#1 is on the right front bank. (you would be surprised at the number of folks who don't catch that after working on Brand G for so long.) With the piston on TDC compression, take the push rod and 'twirl' it between your finger and thumb as you slowly tighten down the bolt. When you feel resistance, STOP!! That is zero lash. Do the same with the other rocker. When you have both at zero lash, back off the bolts a tad and double check. Once you are sure they are both at zero lash, you want to turn each bolt somewhere between half and one turn to be completely tight. 3/4 of a turn is perfect for a street car. Once both valves are shimmed correctly to that adjustment, turn the crank 90 degrees and go to the next cylinder in the firing order. If you do that, the valves will be properly adjusted. I have seen folks adjust valves with just two positions on the crank...but I've seen that method cause problems. My way has never failed me. I suspect you completely collapsed a lifter, then tightened the bolt...which hangs a valve open. This is a common error, especially with new or cleaned lifters. Feeling for resistance eliminates this. You can also lift the push rod up and down with your fingers as you tighten. You will feel the clearance diminish as you get to zero lash and know you are close.

One other thing you should check. If you have had the block decked, heads surfaced, gone to roller rockers, etc, it is possible you could need different length pushrods. This probably has nothing to do with your problem, but make sure the roller is properly positioned on the valve stem. If you don't know how to properly check that, please research what to look for. That can be a disaster waiting to happen otherwise. You sure don't want to drop a valve on your brand new motor.

Lastly, I would quit trying to start this until you know what's wrong. It may be too late already...but you are washing down your cylinders by doing this and you may never get a good ring seal.

Found A problem. The lower to upper intake gasket slid on me and crinkled all up. So now it will idle, not good, but it will idle. Its misfiring pretty bad. And was making great oil pressure, but that went to zero. I suspect something in the perssure port or something clogging the line, i'm taking that out of the block as soon as its cool enough to work on. Just a pretty bad misfire.

Cobraguy, I set all the rocker arms just the way you did, checking each one individually, adding shims accordingly, none took more than a thick and a thin shim. Also i primed the motor and had a friend turn it over a bunch of times to make sure the lifters were full before i set the preload. So now i'm off to figure out the misfire and the oil pressure.

*oil pump was new, as well as a new hardened oil pump shaft. And the lifters arn't ticking, which leads me to believe i still have oil pressure and somethings messing up the cheapo mech. oil pressure gauge i have hooked up.

I had this thought today for you, how much have you changed outside of the engine? Since it could be ignition related, try to put any of those components back on that you replaced. You evidently have the same 140018 coils which I bought, I have heard of new coils not working right to begin with. So without another more obvious thing to check, go back to components which worked before that you have replaced. It's not uncommon to have a bad plug or wire even when new. I plan to test my new coils on my old 302 before the new engine.

All hell breaks loose

So it wasn't an oil pressure gauge problem. I put my oil primer shaft on the pump driveshaft and could spin it by hand. Not good. So the motor is out, trans still in (didn't think i could do it w/out pulling the trans). Found a freeze plug in the bottom of the oil pan. I don't have a balancer puller yet, but i'm pretty sure it came out of the the block behind the timing cover. a 1/4 inch hammer in plug. There was some metal in the oil when i drained it and some chunks stuck to the pick up screen.

All the bearings looked good except for the front which had a small gouge in it. The crank looked good however so i think i cought it in time. No bearings spun.

I'm going to plastigauge the bearings just for my own peace of mind. I also have another oil pump i'm going to put in as well.

I'm not sure if the pump is shot, i took it apart and could really see nothing wrong, i'm wondering if the freeze plug that popped out was letting the oil pressure out into the timing cover and not through the propper passages.

You should see the dents in the fender from me smashing my head into it over all the problems i've been through.

Shoot, there seems to be a theme this week on the forum. Lot's of engine issues happening recently.

Was that a rebuilt engine that has a warantee at all? Those galley plugs are not supposed to come out. They usually either stay until removed, or blow out when not installed properly. Sorry to hear that, I would suspect damage to several things, a lack of oil will at best wear many years of life from an engine. At worst it will not last long at all.

THe coils checked out. They are good coils. Thanks for the help. I'm going on a bit of a vacation for sat/sun, so i should have it done monday/tuesday

I bought the motor from a friend of a friend. Looked good, everything checked out on it, rebuilt, bored, honed .040 pistons, not just rings.

He replaced the plugs on the whole motor, all exterior plugs were brass.

I'm thinking of it right now though, he had thread sealant on all the plugs, threaded and not... and i'm wondering if that had anything to do with those not sticking or staying put. Is anything recommended on the galley plugs as far as sealing up around the plug? Rtv?

are you using some high pressure pump or something. I always lok-tite and stake them in at least 8 places so they dont pop out. Best way is drill and tap the block and install pipe plugs. You might as well remove the lower intake and stake the oil galley plug near the back also.

Most machine shops will use a sealant (not RTV!) to install soft plugs. Actually, what I've seen them use the most is a GM sealant. It's pretty darn good stuff. Coat the bore with sealant and install the plugs. You should never, ever have to stake a properly sized and installed cupped plug. There are millions of them running around without that. If you install the proper plug with the proper tool, it will stay just fine and not leak. If the proper plug doesn't fit correctly, you have a problem with the block and tapping for a pipe plug...if there is sufficient material...is not a bad idea at all.

EDIT: Occasionally, the factory will stake a soft plug. In that case, it should be re-installed that way. But when you stake a plug, you make it darn near impossible to clean up the bore so you can re-install the new plug properly...or you have to remove too much metal to clean it up. In that case, I would toss the soft plugs and go with a tapped plug. But staked plugs are rare.

I still don't think you've found your miss and poor running issue.

I wonder if your valve covers are clearing your roller rockers --if not you will have a valve or two not closing completely