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LEVE 09-05-2001 04:15 PM

Answer to Fuel Injection Test!
OK Gents… Here’s a test to see what you all have learned the last year or so on Fuel Injection[img]/wwwthreads_images/icons/smile.gif[/img]


1. Automatic Transmission swapped out.
2. Jeep was running and under it’s own power went up on ramps and shut off.
3. Transmission was swapped.

Jeep Ignition/fuel specifications:

1. GM HEI ignition.
2. Howell TBI Fuel Injection


1. No start condition.


1. No start….well Duh![img]/wwwthreads_images/icons/crazy.gif[/img]
2. Plugs firing.
3. On start up you can hear the fuel pump cycle 2 seconds and shut off.
4. The fuel pump is not noisy and sounds normal.


Part A. What do you do to diagnose the problem, list your steps?
Part B. What are you’re conclusions as to the problem?
Part C. How long should it take to find the problem?


1. I’ve lead you down the garden path, all the symptoms are correct… but not necessarily right.
2. The problem can be fixed without spending a dime.

The Answer will be given when the thread activity dies down or no one answers… which ever comes first. The The answer will be the steps I followed today to fix the problem.

Prize: None, you’re doing this for fame and glory!

<font color=red>****** Here's the Answer ******</font color=red>

Wow, you guys are good! You’re learning a lot! Years ago I sat down and formulated a set of a basic rules that I’ve used in modification and fabrication of my vehicles. I’ve used these rules as a guide and it’s not let me down. One of the rules is:

<font color=red>A modification, or fabrication, should not be so un-understandable that:
a. One needs to carry manuals to effect the repair.
b. The average backyard mechanic couldn’t figure it out.</font color=red>

When I first installed Fuel Injection I felt that I’d violated the rule (see 1.a above). Six years ago aftermarket fuel injection was expensive, a mystery, and just plain magic as there wasn’t a lot of books or information on the subject. I researched EFI for a year before committing buying a Howell TBI.

After the install I found out I couldn’t be more wrong. EFI is somewhat simple if you learn the basic parts and what each does and the difference between Open loop and Closed Loop operation. It just boils down to logic and troubleshooting skills that each of you has demonstrated so well in diagnosing this problem. Remember each of you is shooting in the dark, you’re not in front of the Jeep so you can only diagnose with the information I gave you. Sometimes that’s just not enough information. I have every confidence each of you who replied would have found the problem right-off.

So on to the fix:

1. Drop back to basics:
a. The TBI is in Open Loop when below about 140* coolant temp, so many of the EFI sensors can’t be blamed for the no-start condition. There are only two sensors involved in Open Loop, the Coolant Temp and the TPS
b. Ground the diagnostic terminal and obtain a 12 code and no others. This confirms the fact that the TBI, sensors and Computer are is working. 12 is an easy number to remember!
2. So then it’s a matter of Air, Fuel, and Timing,
3. The timing had not been disturbed, so it was ruled out, and confirmed the plug had a spark.
4. The TBI gets lots of air, so the problem must be fuel related.
5. The Electric Fuel pump was cycling in Run mode. That is, it turns on for 2 sec and pressurizes the fuel line, then turns off.
6. On start the engine cranks and there is no fuel from the injectors. This was confirmed by tearing a small piece of cardboard and placing it under the injector to see if a spray did occur…. That’s a back up to smelling the raw gas.

Humm…. No gas! But the fuel pump’s cycling? Am I being led down the garden path?

7. Unhook the fuel supply line and cycle the fuel pump.
8. No fuel is emitted during the cycle time. This is curious…. I heard the fuel pump cycle.
9. Remove the fuel pump from its protective PVC canister.
10. Pour gas in a jar on the front passenger’s fender.
11. Connect the fuel pump to the battery… it runs and sounds fine.
12. Attempt to siphon from the jar of gas.
13. Nothing… not even a drop is pumped.
14. Go get the half-used bottle of SeaFoam and pour it in a jar.
15. Siphon the SeaFoam into the fuel pump.
16. Nothing… nadda, zippo, zilch, zero… narry a drop emitted.
17. Continue to let the pump run…. But not too long as an electric fuel pump is cooled by the flow.
18. All of a sudden I hear a “pop” (That’s with ONE “o” folks) and SeaFoam is shooting everywhere out of the pump.
19. Re-insert the siphon into the jar of Gas.
20. Re-connect the pump and pump Gas 4 feet out into the driveway. That was exciting!
21. Reinstall the fuel pump into the PVC Canister.
22. Reconnect the fuel pump lines.
23. Start the Jeep.
24. It started just fine!


The fuel pump had so much varnish in it that it just plain couldn’t function and the outlet was blocked. The fuel treatment SeaFoam had emulsified the blockage and the “pop” that was heard was the blockage being shot out at fuel pump pressure.

<font color=red>Hint to self… never look at the fuel pump straight on when it’s running… it may be loaded… remember the sucking on the sand blaster tube?….</font color=red>

Time to diagnose the repair:

8 minutes

Time to effect the repair:

35 minutes

bluseman2a 09-05-2001 05:00 PM

Re: Test Yourself on Fuel Injection!
Part A. What do you do to diagnose the problem, list your steps?

I'm going to take a shot in the dark and say it's the TPS. You didn't say specifically what tranny is in there now, so I shall assume that you are going from an auto to a manual. Remove it from old location up near the harmonic balancer and put it on the manual bellhousing location (high up on driver's side of BH)? I remember reading something about this but don't know a darned thing about fuel injection. Also try replacing with a new one, in case the old one is bad...

Part B. What are you’re conclusions as to the problem?

Without TPS, engine shuts down the fuel pump.

Part C. How long should it take to find the problem?

About 30 seconds, including time to ask LEVE if you're on the right track

'83 CJ-7 nothing original but the tub and axle tubes

WallyCJ7 09-05-2001 05:04 PM

Re: Test Yourself on Fuel Injection!
1. Spark plugs firing.
2. Installed new tranny
3. Fuel pump works for 2 seconds and sounds normal.

You pinched the fuel line or fuel return line while installing the tranny because the pump doesn’t continually run.

78 CJ7 304V8 Fully locked. Got Rocks?

brendan 09-05-2001 05:20 PM

Re: Test Yourself on Fuel Injection!
How many ramps? If just the front axle is on ramps, did the pint of fuel in the tank slosh back away from the pickup? Start with the simple solutions, right LEVE?

Is the fuel system vapor locked? Problem could be solved without $.10 by properly aligning fuel filter.

You mean Crankshaft Position Sensor(CPS), not Throttle position Sensor(tps), right? Does the howell system even use one? I thought that sensor was only necessary in a multiport setup.


Proud owner of the world's best running Carter BBD

H8monday 09-05-2001 05:34 PM

Re: Test Yourself on Fuel Injection!
Its not a fuel pump or return line, guys. The processor is supposed to shut off the fuel pump after pressurizing, if the engine is not started.

89 YJ
Adversity is imminent, versatility is mandatory, misery is optional.

dave 09-05-2001 06:33 PM

Re: Test Yourself on Fuel Injection!
Question: Is the Howell fuel injection system doing the ignition timing? I've seen Howell now offer there TBI systems with the ability to control spark timing.[img]/wwwthreads_images/icons/smile.gif[/img]

dave 09-05-2001 06:40 PM

Re: Test Yourself on Fuel Injection!
Fuel, Air, Spark, Compression, and correct starter speed are the basic's to get an engine to start.
1. Test fuel pressure? I don't give a damn about the pump noise, I want to know the pressure at the TBI.

2. The ECM supplies a pulsing ground signal to the injectors, with a test light are the injectors being pulsed?

3. Codes, give me codes?

4. How was or was the neutral / park safety switch by-passed?


ExtinctJeep 09-05-2001 10:19 PM

Re: Test Yourself on Fuel Injection!
A deep shot in the dark. Some Auto equiped vehicles came with an ingnition cutoff that prevents the engine from being started in gear. If the new tranny's shifter is misadjusted, then in park, it could think that it is in gear and would defeat the


Jeep...need I say more?

ExtinctJeep 09-05-2001 10:35 PM

Re: Test Yourself on Fuel Injection!

For starters, I will assume that "no start" means that the engine is spinning, but not continuing on its own power (the indication of spark leads me to believe that the distributer is spinning). This rules out starter and starting system.

Plugs firing rules out ignition system.

Fuel pump indicates that the fuel delivery system works, and that the fuel pump has gas (pressure had to be built up somehow).

I would next check that the after delivery fuel system (injectors and sensors) are functioning correctly. I may be able to rule out a faulty O2 as most systems go closed loop when they start. I don't think the throttle postion sensor or crankshaft postion sensor would cause a zero start condition, possibly rough running though.

As most autos (older ones) rely on vacuum to control them, I would check that all the vac lines are connected correctly. If they are missing, then they could cause a lean mix, but it should still start.

The injectors may not be firing. I would check for the smell of gas. If its a TBI, then it should have fuel vapor present at the bore. If there isn't vapor, then I would check for any loose wires or grounding.

Other than these possiblities, I would have to look into the tranny shifter arrangement as I previously stated.

I figure that it could be fixed in under 30 minutes, or longer than an hour.


Jeep...need I say more?

dschwab9 09-05-2001 11:23 PM

Re: Test Yourself on Fuel Injection!
Did you forget to put the speed sensor back on the tranny? Or maybe short something and blow a fuse?

-Derek Schwab
'97 Sidekick Sport
'83 CJ-7

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