I have a 1981 Toyota pickup. The head gasket blew, and we replaced it, which involved:
1) removing lots of parts and disconnecting manifold, hoses and wires (we labeled them to make for easier reconnecting later)
2) replacing the head gasket
3) replacing the valve cover gasket
4) putting all the other stuff, hoses and wires back in place
So now it won’t start.
1) Engine turns over
2) There’s spark
3) Fuel gets to the carb
4) Oil and coolant are staying separate, oil pressure steady
6) Sucking sound from somewhere
5) Occasional detonation/flame from the rear of the engine (after long cranking)
There are lots of things to check, any ideas on where to start? Vaccum? Fuel-air mixture? Timing?
Did you check the head for flatness?
When a cylinder head is removed, especially an aluminum head, a precision straight-edge is placed on the matting face of the head, and a feeler guage is used to measure the flatness of the head. If the feeler guage is able to slip between the straight edge and the face of the head, the head requires machining because the head is warped.
If a warped head is installed, and when the head bolts are torqued, the warped head prevents the proper clamping force to be applied the head gasket. This prevents the fire rings (the metal rings on the head gasket that surround the cylinders) from crushing properly and sealing the cylinders. And when this happens, it results in low compression. Remember, you need air, fuel, spark, and compression in order for an engine to run.
This is a Over Head Cam chain driven engine? If so sounds like to me you have incorrect valve/ignition timing. What repair manual did you use
[quote] Flatness? [quote]
You either have bad cam timing, or a bent valve, or a valve stuck open. IF that wind sound is any indication.
I’m adding it to the woulda-shoulda, may soon be revisited list
The factory service manual and the Clymer Super Shop manuals…one is too specific and hard to follow, the other covers too many model years too vaugely…
Did a dry compression test: 175, 170, 150 and 160 psi. Will do a wet compression test and compare results, but probably not until Sunday.
Maybe your mind is overloaded, and you will find something obvious when you re-check on Sunday. Like spark plug wires in wrong order.
We were really specific and intentional as to wire order - those were the Sharpy-duct tape labels that didn’t wear off with oil.
I’m still concerned about saying the “wind sound” symptom - I would like “pedestrian” to confirm that - they were under the hood while I was cranking.
In my experience, the compression isn’t perfect by the numbers, but it should ignite and idle for a little bit. At least. I mean to make things perfect for a 81 Toyota pick-up is beyond reasonable. We’re just trying to get the thing fired up.
The manuals give some good direction when evaluating with the wet-test and I am very curious to see what happens there. That it won’t start at all bugs me. I mean, assuming timing is off - off big time - will a engine not start at all? Again, in my experience, it usually would start but run rough.
I once put a distributor back in with the rotor 180 degrees off. The engine sounded something like what you report.
Your compression figures suggest that the crankshaft and camshaft are in correct relation to each other. Are you sure you have the #1 cylinder at TDC on the compression (not exhaust) stroke, and the dist rotor pointing close to the post for #1 cylinder’s spark plug wire?
The compression readings are a bit out of spec since one does not want a 25 PSI difference from low to high. If the engine overheated this could be caused by piston rings losing their temper (or spring if you prefer). A wet test will clarify this. However, that compression is good enough to run, although you could wind up with a slightly rough idle or some oil burning if the rings are a bit iffy.
I would re-examine the cam timing and disitributor timing and make double sure the marks are aligned properly; and make sure on the distributor that when you point the rotor at No. 1 that the No. 1 cylinder is at TDC of the compression stroke, not the exhaust stroke.
I didn’t think it was possible to put a distributor on 180 off…
Yes, you can do it, depending on the vehicle. What, exactly, did you do to ensure the cam and distributor were timed correctly? Those are the two obvious possibilities, compression indicates no stuck/bent valves.
We made sure the wires went back in the correct order. The cap was labeled, as well, and I think (?) it only goes on one way. Other than that, we just secured the timing chain to the gear with zip strips as we took it apart and put everything back the way it came apart.
We did a quick test with a straight edge which passed, but in all honesty, if the head was warped the cost to fix wouldn’t have been worth it - it would be on craigslist right now with the line, “warped head - doesn’t start or run - in pieces - you haul - make offer. Caveat emptor!”
I am looking forward to the wet test. But as this is not a primary vehicle, I’m not concerned about 25 PSI. Rough idle and burning oil is fine for this truck - in fact, it’s kinda expected and I would be worried if it wasn’t.
We’ll take a good look at the dist. timing first - the more I read the more I think our issue may be there somewhere.
Thanks all - you guys are great and I will report anything new.
Question on timing. How do you check timing if you can’t get the engine started?
Dist. Cap was on correctly - it was labeled “Top”. Good foresight. We loosened the dist cap adjustment and reset it all one way and tried to get it to start, moving it about 1/16" or 1/32" each time. At some places it seemed to want to start better than others, but it still didn’t start.
It went from one “sucking vacuum noise” to up to two, three and four, but no starting. Various positions would then not have that “sucking vacuum noise” or fewer than before after moving it away and back again. There was a bit of dieseling here and there, but only one revolution and not continuous.
It is getting fuel - we could smell it.
Haven’t done the wet test yet as the compression wasn’t that far off for a truck made when I was in elementary school so we are holding off.
Questions, comments and suggestions are all appreciated. Translation: Please Help!