Help Diagnosing no Start

[betterinwater]

New member here. I have been learning a lot about these vans since I purchased mine a couple of months ago. I cannot say how grateful I am for the info posted by this community, I would have been lost without it. I am the owner of a 1988 4x4 cargo M/T. Since my purchase I have been doing basic recommended maintenance, but generally speaking it has been running well. My most recent project was to redo the cooling system. The radiator looked old and the engine seemed to be getting warmer than it should and so I pulled the radiator and had it recored and in the process also replaced all the hoses, water pump, and fan clutch. Up until the point where I started the cooling system project the van started every time, but a handle full of times it took a bit longer to start (10-15s of cranking). Upon completion of the cooling system restoration my van has been in a no start condition. It cranks fine and I have checked the following in my first round of diagnosis.

-Spark (good looks as expected on two of the plugs, gaps on all four are fine)
-Distributor cap and rotor look good
-Fuel pressure at injector manifold with test connector shorted (a little high 45psi but exactly the same pressure as my friends running 87 van)
-Fuel pressure when cranking without connector shorted (45)
-ECU voltages on 10 and 20 (both 12V so looks like injectors are getting power)
-Diagnostic code reads 51 which on 88 van corresponds to No "IDL", NO "NSW"

I am getting to a point where my knowledge and diagnosing ability is limited. My initial thoughts were the obvious must have forgot to reconnect a connector or vacuum hose that was remove during the cooling system process, but the more time I spend diagnosing and inspecting the engine compartment the less convinced I am of this theory. I also thought maybe the fuel pump as I had one go bad in a similar circumstance but given the tests this seems unlikely.

Is there an easy way to confirm if the injectors are actually spraying?

The diagnostic codes points to the TPS and I am wondering if this could cause a no-start (not even a cough)?

Any other possibilities given the code and conditions?

Thanks for any help you can provide.

[timsrv]

For 88 - 89 vans, a bad coil or igniter usually results in trouble codes 12 or 14. Since you don't have either of those AND you've verified spark, I'd focus on other things. I assume you didn't mess with timing..........right? If you didn't, then it's unlikely a timing issue as it was running before. Fuel pressure is fine, so I'd rule out the pump. This doesn't leave much else. Injectors usually don't clog or fail all at once, so I think I'd want to see if they were getting power. Pull #1 injector connector and put a test light across the terminals of the connector to see if it blinks while cranking. I'd also take a look inside the distributor cap in case it's got moisture on or inside of it. Check that stuff and report back. Tim

[betterinwater]

Thanks Tim, I'm picking up a fuel injector test-light and will be able to continue diagnosing this weekend. My day-job keeps getting in the way of van fun.

Here are some further diagnosis tests I did (before I saw Tim's suggestion):
1) Disconnected TPS sensor. No change, still cranks but no start. Verified a disconnected TPS wouldn't cause a no-start on a friend's '87 van.
2) Probed voltage between No.10 and E01 on the ECU while cranking. The multimeter reads 12.5V when not cranking and about 9.5V while cranking. I'm guessing 9.5V is the average voltage seen by the multimeter (No.10 injector signal is probably "LOW" 25% of the time).
3) Checked many sensor/actuator resistor values. Sensors that were checked include Air Flow Meter, Air Intake Temp Sensor, Water Temperature Sensor, Cold Start Time Switch, Cold Start Injector, and Air Valve. They are all within limits.
4) Sprayed B-12 Carb Cleaner in the air intake during cranking, no change. The spray was more of a squirt and less of a mist; I imagine a mist would have been better. Also, not sure if B-12 is the best substitute for starting fluid...
5) Visually compared my van's spark with a friend's van's spark (his van starts). The spark from my plugs looked just as bright if not brighter than his, but I guess the eye isn't the best judge for that test.

I'll post the results of the test-light test ASAP.

[pinkgrips236]

Do all the fuses check out? I recall having toasted or removed (then forgot to replace) an ignition fuse or a starting fuse...

Can you push / bump start / pop the clutch? Not sure if this will tell you anything important, but you can always just park downhill!

[s_e_a_n_s]

If the spark (and timing) are good, it should fire on starting fluid. I'd verify that as a sanity check. Starting fluid can be sprayed into the intake manifold via a vacuum hose connection as an easy shortcut. Starting fluid is magic (Buy extra - makes an excellent, if very dangerous, solvent/cleaner).

There is an old no-start thread from the 'other site' I found very useful: http://www.toyotavanpeople.com/forum/viewtopic.php?f=9&t=8397&p=60093#p60093

Beyond my depth here, but will offer up for others to correct:
- Make sure whatever state the van is in, air is flowing past the MAF Sensor (MAS, whatever) - and nothing get sprayed in upstream of the MAF - starting fluid being the least harmful exception.
- Checking spark plug (and maybe compression) in #1 cylinder is quick/easy. If you are getting fuel, after a bit of cranking you should likely see/smell gas on plug or in cylinder.

Godspeed.