Proper 5.7 EFI (TBI) compression procedure

Strecker25

Well-Known Member
SILVER Sponsor
Nov 20, 2014
4,905
Rochester, NY
Boat Info
2002 410DA
Engines
Caterpillar 350HP 3126
hi all, what’s the correct way to test compression on a 1998 5.7 EFI with a TBI? I know I need to disable the ignition, I see a lug on the throttle body that looks like it’ll take the lead from the coil, is that the grounding point?

How do I disable the injectors?

I will also dig up my electronic engine manual but I’m not home now. Thanks
 
Hot engine, all plugs out, WOT, unplug dist. and crank sensor and the coil and injectors won't fire. Wouldn't hurt to unplug fuel pump or remove relay. At least 4-5 revolutions on each cylinder or until the gauge stops going up.

I also like a stand alone battery charger hooked up with battery switches on both to maintain steady volts/amps through out the test.
 
Last edited:
Ok cool so pull the connectors at the distributor?

I’ve never actually looked for the cps on these motors. Must be down near the balancer?
 
That's an interesting way to do it. It makes sense since the keys off to the motor none of the ECM or sensors fire up. So the remote switch goes battery positive post directly to large lug on the starter I assume?

Not quite. If you hook anything up to any large lugs, your remote switch better have some heavy gauge cables.

Best bet is to use the remote starter to get power to the small “s” wire on the starter solenoid.

If the solenoid is mounted on the starter, it may be difficult to access and the battery positive is already connected to the large lug on the solenoid.

A remotely mounted solenoid or “slave” May be much easier to access.
 
Maybe I’m misunderstanding you. Are you saying that you hook up the remote stater in such a way as to pass all the necessary current to spin the starter through those light gauge wires on the remote?
 
I see what they’re saying. Hit the slave solenoid with the remote to energize the terminal that is fed by the ignition switch so it will engage slave
 
Last edited:
Just turn your kill switch off. Downside is you have to keep going up to the helm to turn the engine off, of course.
 
Maybe I’m misunderstanding you. Are you saying that you hook up the remote stater in such a way as to pass all the necessary current to spin the starter through those light gauge wires on the remote?
The wire gauge on the two larger slave lugs are a 12 or 14 gauge. Spins no problem with a starter button even with the spark plugs installed. Even less resistance with all plugs removed for a compression test.

This is also a good test if your slave is in question.
 
Ok. When you said “larger lugs” I assumed (there’s that word again) they had the heavy gauge wire, like zero or 2 gauge wire.

Got it now.
 
Used the remote switch to energize the S terminal and it worked great. Numbers are solid too, just cylinder 6 at 170 is a hair low

190 2
180 4
170 6
190 8
190 1
180 3
180 5
190 7
 
Used the remote switch to energize the S terminal and it worked great. Numbers are solid too, just cylinder 6 at 170 is a hair low

190 2
180 4
170 6
190 8
190 1
180 3
180 5
190 7


Good numbers, especially for a 1998
 
Yeah, I was paranoid since I blew a head gasket on the other motor I’ve been doing everything I can to verify this one is healthy and prevent it from blowing.

We discovered the timing wasn’t advancing on the other one, so that may have done it. It went at 3400 rpm. The one that blew had also always generated more iron in its oil samples, so who knows what was going on inside.

On the ‘old’ motor I’ve done plugs, wires, cap, rotor, coil, iac and tps (fixed a stumbling when coming off plane) and soon will do the entire distributor.

I have the fox marine gateways, so the ecm reports timing is advancing but I don’t think that means it actually is...just that the computer is telling it to. Not much left to do for maintenance though, time to just go boating.
 

Forum statistics

Threads
112,945
Messages
1,422,732
Members
60,927
Latest member
Jaguar65
Back
Top