What do you think our problem is?

[matlock]

Alright here is the story, We have just put in the DOHC engine and we are getting spark, and we have fuel, but the engine will not start but it does turn over. It just wont fire, but we can't figure out what the problem is. We have compression ranging from 95-105, what exactly should the compression be? Please if anyone knows what our problem(s) may be please help us out! Thank you

[radrex88]

check the timing.

[matlock]

Ok a quick question, not to sound like a super noob but how do we check our timing if we already tried turning it over???

Thanx do you think Timing is about the only thing wrong with it?

[ryan hagen]

i set the timing up on the motor, all of the "blued" and or "painted" links matched up then i put the dist in and had every theing alighed to tdc number1 and the dist ointing to one, we tried reposition the dist. on its range of adjust ment but still nothing, the only thing i can think of is the compression is low? i would guess 130 to be a service limit but thats a guess amde form my other cars, also i capped the carbon cansiter hose off
"Anyway, capping the charcoal canister hose from the gas tank is not a good idea. The gas tank needs to be ventillated or else the car will not perform correctly..

- Mike"
the car has a s14 intake manifold bolted on but suposedly that doesnt cahnge anything, except some say the idle is is slightly higher???

but anyways ony other thing is when i cleaned the head surface i used brake cleaner so maybe it could have washed all of the oil from the rings????

[Tubed4evr]

Wow that compression is WAY too low. The normal is 180psi and the minimum is 151psi. Either you measured wrong or that is one of the problems.

Ryan

[ryan hagen]

i think its higher, my guess was no oil in the rings, but we got it now after moving the distributor to start but it will rev to like 4000rpm then the idle slowly dies it kinda revs up but then drops like it is trying to relearn its idle....but if i step on the gas and keep it reved up it willlast maybe a minute?? any ideas?

[Bill Roberts]

Time for a full ecu reset.

IS the MAFS clean? No intake leaks? this can confuse the crap out of the ECU and also really look at all the grounds. I know this sounds like a broken record but I had problems once everything was set-up right and traced it to a bad ground wire. Go figga..

[mbmbmb23]

Fuel filter? Injectors? Did you replace the plugs and wires but forget to gap the plugs?




-m

[ryan hagen]

we added a bunch of 4 gauge grounds that were extras, the car wasnt run since febuary...
we drove it back from chicago and the the cam stopped gettin oil cause the used car palce didnt really change it and the cam seized up.
so i took the motor out, repalced all the seals and gaskets (crank, oil pan, head gasket etc), and got a newer head.
then come the mods

1. new valves,new guides,new valve seals, and new springs, then i took out all the casting marks in the ports
2. pdm stage 2 cams
3. s14 upper inatke manifold. i only used the upper and put my s13 lower with all the s13 sensors on it back on.(simplified the butterfly removal)
4. egr and aiv removal
5.cold air intake
6.pace setter header, and punched out cat
7. denso iriduim spark plugs
8. UR carnk pulley
9. aluminum fly wheel with centerforce daul friction clutch
10. new cap and rotor, new plug wires
any idea if any of this could have messed it up much?
suprising ly when i reved it up it didnt back fire hardly at all with a open header, maybe one pop on several starts.

[Bill Roberts]

You are going to have to try some wild timing on the fly. Could you have the engine inverse stroke?

It certainly points to timing...but when it does fire off, you will have a mean mofo on the loose.

See, mainly when an engine does this..TDC is not hitting TDC but hitting inverse Top. I discovered this on my first car, the venerable plymouth valiant slant six.

Since it is a 4 stroke engine..you could be half way into the stroke and not top dead center for zero. It can all look right..but be out 1/2.

If this does not make any sense, I apologize in advance...as it may be physically impossable to be 2 stroks off on a 4 stroke SR...but then again..I have seen this happen a few times with other engines..and they try their best to run. One old mopar engine actually tryed to run backwards (dieseling)

Long shot, dont flame me but worth looking into. IF you have compression, timing, fire, fuel...correct gas/air mix..it WILL run.

[240racer]

Originally posted by ryan hagen
we tried reposition the dist. on its range of adjust ment but still nothing,

just take the two bolts out completly, then you can turn the dist all the way around while cranking and watching with a timing light. Then once you get close, put the bolts back in.

[ryan hagen]

well the timing has to be close, cause it will run for short bursts but im gonna take it in to nissan dealer ship on tuesday if i cant figure it out, i hate to pay the 75$ a hour but they know those motors way better than i do......

[ryan hagen]

we already did that then when we ran out of adjustment we had to take the dist out and move it one tooth but then it only lasted a few more seconds, we would hit the bolts right next to the dist on the right side of the dist so we had to move it over the one tooth

[240racer]

about the dealership plan, my brother and I have been trying to get his Audi 90 running for a while now, and we finally broke down and towed it to the dealer so they could run their computers on it and figure out what's wrong. All they told us was stuff we knew already. Like, has fuel pressure, no spark. So they suggested that he buy a new computer and coil and try that to see if it fixes it. That's all they had, it was super dumb. They charged him $200 for that. Then it was going to be about $2000 for the computer and coil so the could "check" and see if that fixes it. We can buy a computer and coil and check and see if it starts. Anyway, that made me loose all faith in bringing old cars to dealers. They just want to work on new RS6's and I don't blame them.

[ryan hagen]

i know the mechanics at the dealer ship in town, 2 of them are race car guys, and they race a celica and a nissan truck,they dont really race them they build them and then find a driver. the nissan truck they built is pretty bad *** i guess, but they have been givin me advice and might even give me a deal on laybor.
but none-the-less i d rather get it goin with me and my friends,

[sykikchimp]

Originally posted by Bill Roberts
You are going to have to try some wild timing on the fly. Could you have the engine inverse stroke?

It certainly points to timing...but when it does fire off, you will have a mean mofo on the loose.

See, mainly when an engine does this..TDC is not hitting TDC but hitting inverse Top. I discovered this on my first car, the venerable plymouth valiant slant six.

Since it is a 4 stroke engine..you could be half way into the stroke and not top dead center for zero. It can all look right..but be out 1/2.

If this does not make any sense, I apologize in advance...as it may be physically impossable to be 2 stroks off on a 4 stroke SR...but then again..I have seen this happen a few times with other engines..and they try their best to run. One old mopar engine actually tryed to run backwards (dieseling)



So what your saying is the exhaust valves are opening at while the injectors are firing? seems it would definately try to run backwards that way, it would just be fighting the starter and transmission.

I would double check your compression, and verify what it is. If it's still low, run a leak down test. That will tell you were your loosing the pressure in the chamber from.