New Member needs help-'94 B2300 Won't Start

[regerton]

I've had my '94 B2300 about a year. Bought it from a friend to help him out. He was the original owner, I'm second owner. About a year before I bought it, he had the water pump and radiator replaced. Otherwise only normal maintenance has been needed. I drove the truck occasionally for most of a year. My youngest daughters car played out, so she started driving the B2300. All was well for several months, then she reported that about 15 miles into her 20 mile drive to work, it began to run hotter than normal, but not over-heating. The heat guage would go up to about 3/4's scale instead of less than 1/2 scale as usual. Her husband began checking the coolant level and found it necessary to add 1-2 quarts very 7-10 days. But, could find no evidence of coolant leaking around the radiator, hoses, overflow, heater core in dashboard, or around/under the engine block. The fan and fan clutch seem to be working normally. So, for several months she drove it to work, when the temp guage would begin to rise, she'd throw the heater control lever to HOT, and get to work at about 3/4's scale on the temp guage. Every 7-10 days 1-2 quarts of coolant were added. Had my son-in-law pull one plug from each cylinder on the air filter side of the engine, checking for coolant buildup on the plugs and he reported them to look 100% normal. Also, no coolant has been found in the oil, or oil in the coolant.
Lastly, here's where the real problem starts, she arrived home one evening, everything normal, temp guage at 3/4's, heater control lever at full HOT.
The next morning, the truck wouldn't start! It turned over fine, just wouldn't fire.
I have since brought it home and check out the following;
-Spark- removed all four plugs on the air filter side of the engine, connected one plug to it's cable, held it against the head and had my wife crank the engine. I got a fine spark in the plug. In fact, the other cylinders blew out a reddish flame almost a foot long! So I know it's getting gas! I have also checked the fuel pump emergency shut-off switch (it's set properly) and the fuel pump runs when the ignition switch is turned on.
-Checked the timing belt by turning the crankshaft pulley with a socket wrench while my wife (she's a good mechanics helper, and that's a good thing!) watched the cam pulley turn. Belt's not broken. I lined up the TDC mark on the crank pulley and she saw the cam pulley marks line up. I turned the crank pulley another turn, she watched the cam pulley turn and when TDC was lined up the second time, she saw no timing marks on the cam pulley. Cam timing looks OK.
-Compression check- I have an about 30 yr old compression guage. It has the rubber cone on the end for a quick compression check. I measured each cylinder at about 25psi. I have a '76 Chevy P/U with a '97 G.M. crate engine in it, it measured 100psi on a couple of cylinders on that P/U the same afternoon, with the same guage.
I need some help figuring out what I need to do get this B2300 running again.
Sorry for the long story, but I wanted to give as much detail as I could.
Thanks in advance,
Ray

[89B2200]

Hello Ray,

Safety first.
When you are testing for spark or compression, make sure you disable the fuel pump.
Otherwise you may have a serious engine fire.

Your compression test seemed a little low. It is not enough to get your engine going.
Perform a leakdown test to validate the low compression readings.
You could have a blown headgasket forcing exhaust gases into your cooling system thus pressurizing it.
Excessive cooling system pressure could be leaking out of the of the overflow reservoir while motor was running.

[mazdatech]

very low compression...u need 150 give or take some. with less then 20% variation between cylinders, borrow a friends comp gauge and verify yours. Also a leak down test as 892200 said is valuable, repost with more info for more diag.

[regerton]

Originally Posted by 89B2200

Hello Ray,

Safety first.
When you are testing for spark or compression, make sure you disable the fuel pump.
Otherwise you may have a serious engine fire.

Your compression test seemed a little low. It is not enough to get your engine going.
Perform a leakdown test to validate the low compression readings.
You could have a blown headgasket forcing exhaust gases into your cooling system thus pressurizing it.
Excessive cooling system pressure could be leaking out of the of the overflow reservoir while motor was running.

- Thanks for the help.
I'm an old airplane mechanic. My Compression Guage Kit is from the early '70's and is a kit for airplane engines. The sparkplug adaptors have a square shoulder, depending on a 'crush' type copper seal. I'm just going to invest in a new compression guage kit (or try to rent one) to do the leak down test.
I'll post my findings and the ultimate fix.
Again, thanks,
Ray

[regerton]

Originally Posted by mazdatech

very low compression...u need 150 give or take some. with less then 20% variation between cylinders, borrow a friends comp gauge and verify yours. Also a leak down test as 892200 said is valuable, repost with more info for more diag.

Thanks for your help.
On my Chevy P/U I expected 125-175psi. My aged guage showed 100 and that truck runs fine. I suspect my old guage may be getting weak in the service.
I post my compression findings and looks like I'm going to be pulling the head, so I'll post the final findings, too.
Thanks,
Ray